Denial of Service
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
How It Works
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions. Attackers exploit asymmetry: minimal attacker effort produces disproportionate resource consumption on the target. Application-level attacks use specially crafted inputs that trigger expensive operations—a regex engine processing malicious patterns can backtrack exponentially, or XML parsers recursively expand entities until memory exhausts. Network-level attacks flood targets with connection requests or amplify traffic through reflection, but application vulnerabilities often provide the most efficient attack surface.
The attack typically begins with reconnaissance to identify resource-intensive operations or unprotected endpoints. For algorithmic complexity attacks, adversaries craft inputs hitting worst-case performance—hash collision inputs filling hash tables with collisions, deeply nested JSON triggering recursive parsing, or pathological regex patterns like (a+)+b against strings of repeated 'a' characters. Resource exhaustion attacks open thousands of connections, upload massive files to unbounded storage, or trigger memory leaks through repeated operations. Crash-based attacks target error handling gaps: null pointer dereferences, unhandled exceptions in parsers, or assertion failures that terminate processes.
Impact
- Service unavailability preventing legitimate users from accessing applications during attack duration
- Revenue loss from downtime in e-commerce, SaaS platforms, or transaction processing systems
- Cascading failures as resource exhaustion spreads to dependent services or database connections pool out
- SLA violations triggering financial penalties and damaging customer trust
- Security team distraction providing cover for data exfiltration or intrusion attempts running concurrently
Real-World Examples
CVE-2018-1000544 in Ruby's WEBrick server allowed ReDoS through malicious HTTP headers containing specially crafted patterns that caused the regex engine to backtrack exponentially, freezing request processing threads. A single attacker could saturate all available workers.
Cloudflare experienced a global outage in 2019 when a single WAF rule containing an unoptimized regex hit pathological cases on legitimate traffic spikes. The .*(?:.*=.*)* pattern exhibited catastrophic backtracking, consuming CPU cycles across their edge network until the rule was disabled.
CVE-2013-1664 demonstrated XML bomb vulnerabilities in Python's XML libraries. Attackers uploaded XML documents with nested entity definitions-each entity expanding to ten copies of the previous level. A 1KB upload could expand to gigabytes in memory during parsing, crashing applications instantly.
Mitigation
- Strict input validation enforcing size limits, complexity bounds, and nesting depth restrictions before processing
- Request rate limiting per IP address, API key, or user session with exponential backoff
- Timeout enforcement terminating operations exceeding reasonable execution windows (typically 1-5 seconds)
- Resource quotas limiting memory allocation, CPU time, and connection counts per request or tenant
- Regex complexity analysis using linear-time algorithms or sanitizing patterns to eliminate backtracking
- Circuit breakers automatically rejecting requests when error rates or latency thresholds indicate degradation
- Load balancing and autoscaling distributing traffic across instances with automatic capacity expansion
Recent CVEs (40181)
The "nickname" field within Savoir-faire Linux's Jami application is susceptible to a failed state when a user inserts special characters into the field. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
Issue summary: The AES-SIV cipher implementation contains a bug that causes it to ignore empty associated data entries which are unauthenticated as a consequence. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
iSCSI dissector crash in Wireshark 4.0.0 to 4.0.6 allows denial of service via packet injection or crafted capture file. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Kafka dissector crash in Wireshark 4.0.0 to 4.0.6 and 3.6.0 to 3.6.14 allows denial of service via packet injection or crafted capture file. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
libjpeg commit db33a6e was discovered to contain a heap buffer overflow via LineBitmapRequester::EncodeRegion at linebitmaprequester.cpp. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
libjpeg commit db33a6e was discovered to contain a reachable assertion via BitMapHook::BitMapHook at bitmaphook.cpp. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A Cross Site Request Forgery (CSRF) vulnerability in issabel-pbx v.4.0.0-6 allows a remote attacker to cause a denial of service via the delete new virtual fax function. Rated medium severity (CVSS 4.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and no vendor patch available.
Envoy is a cloud-native high-performance edge/middle/service proxy. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
cmark-gfm is an extended version of the C reference implementation of CommonMark, a rationalized version of Markdown syntax with a spec. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
mx-chain-go is the official implementation of the MultiversX blockchain protocol, written in golang. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Uncontrolled Resource Consumption vulnerability could allow attackers to cause denial of service by exhausting system resources.
Incorrect signature verification of the firmware during the Device Firmware Update process of Belkin Wemo Smart Plug WSP080 v1.2 allows attackers to cause a Denial of Service (DoS) via a crafted. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
Controller DoS due to buffer overflow in the handling of a specially crafted message received by the controller. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Duktape is an 3rd-party embeddable JavaScript engine, with a focus on portability and compact footprint. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Specially crafted string can cause a buffer overrun in the JSON parser library leading to a crash of the Zabbix Server or a Zabbix Proxy. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
JavaScript preprocessing, webhooks and global scripts can cause uncontrolled CPU, memory, and disk I/O utilization. Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
An issue has been discovered in GitLab CE/EE affecting all versions starting from 10.3 before 15.11.10, all versions starting from 16.0 before 16.0.6, all versions starting from 16.1 before 16.1.1. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in Qt before 5.15.15, 6.x before 6.2.10, and 6.3.x through 6.5.x before 6.5.3. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
In incfs_kill_sb of fs/incfs/vfs.c, there is a possible memory corruption due to a use after free. Rated medium severity (CVSS 6.7), this vulnerability is low attack complexity.
there is a possible out of bounds read due to a missing bounds check. Rated high severity (CVSS 7.2), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
In multiple functions of binder.c, there is a possible memory corruption due to a use after free. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
In validateForCommonR1andR2 of PasspointConfiguration.java, there is a possible way to inflate the size of a config file with no limits due to a buffer overflow. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. This Buffer Copy without Size Check vulnerability could allow attackers to overflow a buffer to corrupt adjacent memory.
In Policy of Policy.java, there is a possible boot loop due to resource exhaustion. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. This Uncontrolled Resource Consumption vulnerability could allow attackers to cause denial of service by exhausting system resources.
GzipSource does not handle an exception that might be raised when parsing a malformed gzip buffer. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
A flaw was found in libtiff. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
During the worker lifecycle, a use-after-free condition could have occurred, which could have led to a potentially exploitable crash. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The session restore helper crashed whenever there was no parameter sent to the message handler. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Where this vulnerability exists in the Rockwell Automation 1756-EN4* Ethernet/IP communication products, it could allow a malicious user to cause a denial of service by asserting the target system. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue discovered in MikroTik Router v6.46.3 and earlier allows attacker to cause denial of service via misconfiguration in the SSH daemon. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
Apache Airflow, versions before 2.6.3, has a vulnerability where an authenticated user can use crafted input to make the current request hang. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
A NULL pointer dereference vulnerability was found in netlink_dump. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
In iwnpi server, there is a possible out of bounds write due to a missing bounds check. Rated medium severity (CVSS 4.4), this vulnerability is low attack complexity. No vendor patch available.
In hci_server, there is a possible out of bounds read due to a missing bounds check. Rated medium severity (CVSS 4.4), this vulnerability is low attack complexity. No vendor patch available.
In FM service, there is a possible missing params check. Rated medium severity (CVSS 4.4), this vulnerability is low attack complexity. No vendor patch available.
In libimpl-ril, there is a possible out of bounds write due to a missing bounds check. Rated medium severity (CVSS 4.4), this vulnerability is low attack complexity. No vendor patch available.
In libimpl-ril, there is a possible out of bounds write due to a missing bounds check. Rated medium severity (CVSS 4.4), this vulnerability is low attack complexity. No vendor patch available.
An issue was discovered in function get_gnu_verneed in rizinorg Rizin prior to 0.5.0 verneed_entry allows attackers to cause a denial of service via crafted elf file. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity.
Null pointer dereference vulnerability exists in multiple vendors MFPs and printers which implement Debut web server 1.2 or 1.3. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Windows CryptoAPI Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Uncontrolled Resource Consumption vulnerability could allow attackers to cause denial of service by exhausting system resources.
Windows Peer Name Resolution Protocol Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.
Windows Local Security Authority (LSA) Denial of Service Vulnerability. Rated medium severity (CVSS 6.5), this vulnerability is no authentication required, low attack complexity.
Windows Extended Negotiation Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Windows Authentication Denial of Service Vulnerability. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. This Uncontrolled Resource Consumption vulnerability could allow attackers to cause denial of service by exhausting system resources.
Windows Deployment Services Denial of Service Vulnerability. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.
HTTP.sys Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Uncontrolled Resource Consumption vulnerability could allow attackers to cause denial of service by exhausting system resources.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.
HTTP.sys Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.
Microsoft Message Queuing (MSMQ) Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.
Microsoft Message Queuing (MSMQ) Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.
Remote Procedure Call Runtime Denial of Service Vulnerability. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.
A flaw was found in the QEMU built-in VNC server. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.
Cross Site Request Forgery (CSRF) vulnerability in issabel-pbx v.4.0.0-6 allows a remote attacker to cause a denial of service via the delete user grouplist function. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
Cross Site Request Forgery (CSRF) vulnerability in issabel-pbx v.4.0.0-6 allows a remote attacker to cause a denial of service via a crafted script to the deleteuser function. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A flaw was found in the subsequent get_user_pages_fast in the Linux kernel’s interface for symmetric key cipher algorithms in the skcipher_recvmsg of crypto/algif_skcipher.c function. Rated medium severity (CVSS 4.7).
Buffer Overflow vulnerability in Avast AntiVirus before v.19.7 allows a local attacker to cause a denial of service via a crafted request to the aswSnx.sys driver. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. This Buffer Copy without Size Check vulnerability could allow attackers to overflow a buffer to corrupt adjacent memory.
A vulnerability has been identified in SIMATIC MV540 H (All versions < V3.3.4), SIMATIC MV540 S (All versions < V3.3.4), SIMATIC MV550 H (All versions < V3.3.4), SIMATIC MV550 S (All versions <. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability has been identified in SIMATIC MV540 H (All versions < V3.3.4), SIMATIC MV540 S (All versions < V3.3.4), SIMATIC MV550 H (All versions < V3.3.4), SIMATIC MV550 S (All versions <. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability has been identified in SIMATIC MV540 H (All versions < V3.3.4), SIMATIC MV540 S (All versions < V3.3.4), SIMATIC MV550 H (All versions < V3.3.4), SIMATIC MV550 S (All versions <. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
SAP SQL Anywhere - version 17.0, allows an attacker to prevent legitimate users from accessing the service by crashing the service. Rated high severity (CVSS 7.1), this vulnerability is low attack complexity. No vendor patch available.
A heap buffer overflow vulnerability was found in sox, in the lsx_readbuf function at sox/src/formats_i.c:98:16. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A security defect was identified that enabled a user of Foundry Issues to perform a Denial of Service attack by submitting malformed data in an Issue that caused loss of frontend functionality to all. Rated high severity (CVSS 7.7), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
A heap buffer overflow vulnerability was found in sox, in the startread function at sox/src/hcom.c:160:41. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
A floating point exception vulnerability was found in sox, in the read_samples function at sox/src/voc.c:334:18. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
A floating point exception vulnerability was found in sox, in the lsx_aiffstartwrite function at sox/src/aiff.c:622:58. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
A vulnerability was found in wallabag 2.5.4. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and no vendor patch available.
IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) 10.5, 11.1, and 11.5 is vulnerable to denial of service with a specially crafted query. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
IBM DB2 for Linux, UNIX and Windows (includes Db2 Connect Server) 10.5, 11.1, and 11.5 is vulnerable to denial of service with a specially crafted query on certain tables. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) 10.5, 11.1, and 11.5 is vulnerable to denial of service with a specially crafted query on certain tables. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) 10.5, 11.1, and 11.5 is vulnerable to denial of service with a specially crafted query on certain tables. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) 10.5, 11.1, and 11.5 is vulnerable to denial of service with a specially crafted query on certain tables. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) 11.1 and 11.5 federated server is vulnerable to a denial of service as the server may crash when using a specially crafted wrapper. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
IBM Watson Knowledge Catalog on Cloud Pak for Data 4.0 could allow an authenticated user send a specially crafted request that could cause a denial of service. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
IBM Watson CP4D Data Stores 4.6.0 does not properly allocate resources without limits or throttling which could allow a remote attacker with information specific to the system to cause a denial of. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The bluetooth HCI host layer logic not clearing a global reference to a state pointer after handling connection events may allow a malicious HCI Controller to cause the use of a dangling reference in. Rated high severity (CVSS 8.0), this vulnerability is low attack complexity. No vendor patch available.
Deserialization of Untrusted Data vulnerability in Apache Software Foundation Apache Johnzon. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Mastodon is a free, open-source social network server based on ActivityPub. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Allocation of Resources Without Limits vulnerability could allow attackers to exhaust system resources through uncontrolled allocation.
Mastodon is a free, open-source social network server based on ActivityPub. Rated critical severity (CVSS 9.9), this vulnerability is remotely exploitable, low attack complexity. This Path Traversal vulnerability could allow attackers to access files and directories outside the intended path.
An access violation vulnerability exists in the eventcore functionality of Milesight UR32L v32.3.0.5. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
Vulnerability of incomplete input parameter verification in the communication framework module. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Stack out-of-bounds write vulnerability in IpcRxImeiUpdateImeiNoti of RILD priro to SMR Jul-2023 Release 1 cause a denial of service on the system. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
A divide by zero issue discovered in Kodi Home Theater Software 19.5 and earlier allows attackers to cause a denial of service via use of crafted mp3 file. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.