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 (40243)
An issue was discovered in cp-demangle.c in GNU libiberty, as distributed in GNU Binutils 2.31. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
An issue was discovered in cp-demangle.c in GNU libiberty, as distributed in GNU Binutils 2.31. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
An issue was discovered in LibTIFF 4.0.9. 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.
When FW tries to get random mac address generated from new SW RNG and ADC values read are constant then DUT get struck in loop while trying to get random ADC samples in Snapdragon Mobile in version. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
When a series of FDAL messages are sent to the modem, a Use After Free condition can occur in Snapdragon Automobile, Snapdragon Mobile, Snapdragon Wear in version MDM9206, MDM9607, MDM9640, MDM9650,. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
An issue was discovered in Xpdf 4.00. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
An issue was discovered in Xpdf 4.00. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
ServersCheck Monitoring Software through 14.3.3 allows local users to cause a denial of service (menu functionality loss) by creating an LNK file that points to a second LNK file, if this second LNK. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and no vendor patch available.
Splunk Enterprise 6.2.x before 6.2.14, 6.3.x before 6.3.10, 6.4.x before 6.4.7, and 6.5.x before 6.5.3; and Splunk Light before 6.6.0 allow remote attackers to cause a denial of service via a crafted. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Splunkd in Splunk Enterprise 6.2.x before 6.2.14 6.3.x before 6.3.11, and 6.4.x before 6.4.8; and Splunk Light before 6.5.0 allow remote attackers to cause a denial of service via a malformed HTTP. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The Mitel MiVoice 5330e VoIP device is affected by memory corruption flaws in the SIP/SDP packet handling functionality. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
An issue was discovered in elf_link_input_bfd in elflink.c in the Binary File Descriptor (BFD) library (aka libbfd), as distributed in GNU Binutils 2.31. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
An issue was discovered in the merge_strings function in merge.c in the Binary File Descriptor (BFD) library (aka libbfd), as distributed in GNU Binutils 2.31. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A heap-based buffer over-read issue was discovered in the function sec_merge_hash_lookup in merge.c in the Binary File Descriptor (BFD) library (aka libbfd), as distributed in GNU Binutils 2.31,. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A KERedirect Untrusted Pointer Dereference Privilege Escalation vulnerability in Trend Micro Antivirus for Mac (Consumer) 7.0 (2017) and above could allow a local attacker to escalate privileges on. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
A KERedirect Untrusted Pointer Dereference Privilege Escalation vulnerability in Trend Micro Antivirus for Mac (Consumer) 7.0 (2017) and above could allow a local attacker to escalate privileges on. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
A KERedirect Untrusted Pointer Dereference Privilege Escalation vulnerability in Trend Micro Antivirus for Mac (Consumer) 7.0 (2017) and above could allow a local attacker to escalate privileges on. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
A ctl_set KERedirect Untrusted Pointer Dereference Privilege Escalation vulnerability in Trend Micro Antivirus for Mac (Consumer) 7.0 (2017) and above could allow a local attacker to escalate. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
chmd_read_headers in mspack/chmd.c in libmspack before 0.8alpha accepts a filename that has '\0' as its first or second character (such as the "/\0" name). Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
Open Design Alliance Drawings SDK 2019Update1 has a vulnerability during the reading of malformed files, allowing attackers to obtain sensitive information from process memory or cause a crash. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
IMFCameraProtect.sys in IObit Malware Fighter 6.2 (and possibly lower versions) is vulnerable to a stack-based buffer overflow. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. Public exploit code available and no vendor patch available.
Divide-by-zero vulnerabilities in the function arlib_add_symbols() in arlib.c in elfutils 0.174 allow remote attackers to cause a denial of service (application crash) with a crafted ELF file, as. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
An Invalid Memory Address Dereference exists in the function elf_end in libelf in elfutils through v0.174. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
Spring Framework, version 5.1, versions 5.0.x prior to 5.0.10, versions 4.3.x prior to 4.3.20, and older unsupported versions on the 4.2.x branch provide support for range requests when serving. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
The get_count function in cplus-dem.c in GNU libiberty, as distributed in GNU Binutils 2.31, allows remote attackers to cause a denial of service (malloc called with the result of an. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
An issue was discovered in libpg_query 10-1.0.2. 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 vulnerability can occur when capturing a media stream when the media source type is changed as the capture is occurring. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A potentially exploitable crash in TransportSecurityInfo used for SSL can be triggered by data stored in the local cache in the user profile directory. Rated high severity (CVSS 7.0). No vendor patch available.
A use-after-free vulnerability can occur when an IndexedDB index is deleted while still in use by JavaScript code that is providing payload values to be stored. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A use-after-free vulnerability can occur when refresh driver timers are refreshed in some circumstances during shutdown when the timer is deleted while still in use. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A use-after-free vulnerability can occur when script uses mutation events to move DOM nodes between documents, resulting in the old document that held the node being freed but the node still having a. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An integer overflow can occur during graphics operations done by the Supplemental Streaming SIMD Extensions 3 (SSSE3) scaler, resulting in 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.
An integer overflow can occur in the SwizzleData code while calculating buffer sizes. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A use-after-free vulnerability can occur when deleting an input element during a mutation event handler triggered by focusing that element. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The function DCTStream::getBlock in Stream.cc in Xpdf 4.00 allows remote attackers to cause a denial of service (NULL pointer dereference) via a crafted pdf file, as demonstrated by pdftoppm. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
The function DCTStream::decodeImage in Stream.cc in Xpdf 4.00 allows remote attackers to cause a denial of service (NULL pointer dereference) via a crafted pdf file, as demonstrated by pdftoppm. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
The function DCTStream::readScan in Stream.cc in Xpdf 4.00 allows remote attackers to cause a denial of service (NULL pointer dereference) via a crafted pdf file, as demonstrated by pdftoppm. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
The function Object::isName() in Object.h (called from Gfx::opSetFillColorN) in Xpdf 4.00 allows remote attackers to cause a denial of service (stack-based buffer over-read) via a crafted pdf file,. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
The GfxImageColorMap class in GfxState.cc in Xpdf 4.00 allows remote attackers to cause a denial of service (heap-based buffer over-read) via a crafted pdf file, as demonstrated by pdftoppm. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
CCITTFaxStream::readRow() in Stream.cc in Xpdf 4.00 allows remote attackers to cause a denial of service (heap-based buffer over-read) via a crafted pdf file, as demonstrated by pdftoppm. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A vulnerability in the Control and Provisioning of Wireless Access Points (CAPWAP) protocol component of Cisco Wireless LAN Controller (WLC) Software could allow an unauthenticated, remote attacker. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability in the 802.11r Fast Transition feature set of Cisco IOS Access Points (APs) Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on. Rated high severity (CVSS 7.4), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
A vulnerability in the Cisco Aironet Series Access Points (APs) software could allow an authenticated, adjacent attacker to cause an affected device to reload unexpectedly, resulting in a denial of. Rated medium severity (CVSS 6.8), this vulnerability is low attack complexity. No vendor patch available.
A vulnerability in the Precision Time Protocol (PTP) feature of Cisco Nexus 5500, 5600, and 6000 Series Switches running Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause. Rated high severity (CVSS 8.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability in the Simple Network Management Protocol (SNMP) input packet processor of Cisco NX-OS Software could allow an authenticated, remote attacker to cause the SNMP application of an. Rated high severity (CVSS 7.7), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
A vulnerability in the Link Layer Discovery Protocol (LLDP) implementation for Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a denial of. Rated medium severity (CVSS 5.3), this vulnerability is no authentication required. No vendor patch available.
Adobe Digital Editions versions 4.5.8 and below have an use after free vulnerability. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A stack-based buffer over-read exists in setbit() at iptree.h of TCPFLOW 1.5.0, due to received incorrect values causing incorrect computation, leading to denial of service during an. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A use-after-free was discovered in the tcpbridge binary of Tcpreplay 4.3.0 beta1. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Use After Free vulnerability could allow attackers to access freed memory to execute arbitrary code or crash the application.
A heap-based buffer over-read was discovered in the tcpreplay-edit binary of Tcpreplay 4.3.0 beta1, during the incremental checksum operation. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Text component of Oracle Database Server. Rated high severity (CVSS 8.2), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: Server: Windows). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: InnoDB). Rated medium severity (CVSS 4.4), this vulnerability is remotely exploitable.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: Server: Logging). Rated medium severity (CVSS 4.4), this vulnerability is remotely exploitable.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: Server: Storage Engines). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: Server: JSON). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: Server: Security: Roles). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: Server: RBR). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: InnoDB). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: Server: Memcached). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: Kernel). Rated medium severity (CVSS 5.7), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: Kernel Zones Virtualized NIC Driver). Rated medium severity (CVSS 6.2), this vulnerability is no authentication required, low attack complexity.
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: Kernel Zones). Rated medium severity (CVSS 5.3).
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: Kernel). Rated low severity (CVSS 1.8).
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: SMB Server). Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: SMB Server). Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: Verified Boot). Rated low severity (CVSS 3.9).
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: Zones). Rated medium severity (CVSS 4.9), this vulnerability is no authentication required.
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: Kernel). Rated medium severity (CVSS 4.4), this vulnerability is low attack complexity.
Vulnerability in the Solaris component of Oracle Sun Systems Products Suite (subcomponent: Sudo). Rated medium severity (CVSS 5.6), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the Oracle Virtual Directory component of Oracle Fusion Middleware (subcomponent: Virtual Directory Manager). Rated high severity (CVSS 8.5), this vulnerability is remotely exploitable.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: InnoDB). Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: Server: Merge). Rated medium severity (CVSS 5.5), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology component of Oracle Fusion Middleware (subcomponent: Outside In Filters). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.