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 (40225)
Vulnerability in the Oracle GraalVM Enterprise Edition product of Oracle GraalVM (component: LLVM Interpreter). Rated high severity (CVSS 7.7), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Oracle VM VirtualBox product of Oracle Virtualization (component: Core). Rated medium severity (CVSS 6.0), this vulnerability is low attack complexity.
Vulnerability in the Java SE, Java SE Embedded product of Oracle Java SE (component: Serialization). Rated low severity (CVSS 3.7), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Java SE, Java SE Embedded product of Oracle Java SE (component: JAXP). Rated low severity (CVSS 3.7), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the Java SE, Java SE Embedded product of Oracle Java SE (component: Networking). Rated low severity (CVSS 3.7), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the Java SE product of Oracle Java SE (component: Hotspot). Rated medium severity (CVSS 4.8), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the Java SE, Java SE Embedded product of Oracle Java SE (component: Scripting). Rated medium severity (CVSS 4.8), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Java SE, Java SE Embedded product of Oracle Java SE (component: JAXP). Rated low severity (CVSS 3.7), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the Oracle Outside In Technology product of Oracle Fusion Middleware (component: Outside In Filters). Rated high severity (CVSS 7.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology product of Oracle Fusion Middleware (component: Outside In Filters). Rated high severity (CVSS 7.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology product of Oracle Fusion Middleware (component: Outside In Filters). Rated high severity (CVSS 7.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the MySQL Server product of Oracle MySQL (component: InnoDB). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Java SE, Java SE Embedded product of Oracle Java SE (component: Concurrency). Rated low severity (CVSS 3.7), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the MySQL Server product of Oracle MySQL (component: InnoDB). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Java SE, Java SE Embedded product of Oracle Java SE (component: 2D). Rated low severity (CVSS 3.7), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the Oracle Solaris product of Oracle Systems (component: SMF services & legacy daemons). Rated low severity (CVSS 3.6).
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Replication). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Security: Encryption). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Core RDBMS (jackson-databind) component of Oracle Database Server. Rated medium severity (CVSS 5.7), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Core RDBMS component of Oracle Database Server. Rated low severity (CVSS 3.9), this vulnerability is low attack complexity.
Vulnerability in the Core RDBMS component of Oracle Database Server. Rated low severity (CVSS 3.9), this vulnerability is low attack complexity.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: PS). Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Java SE, Java SE Embedded product of Oracle Java SE (component: Networking). Rated low severity (CVSS 3.1), this vulnerability is remotely exploitable, no authentication required.
Vulnerability in the Oracle VM VirtualBox product of Oracle Virtualization (component: Core). Rated high severity (CVSS 7.3), this vulnerability is low attack complexity.
Vulnerability in the MySQL Server product of Oracle MySQL (component: InnoDB). Rated medium severity (CVSS 4.4), this vulnerability is remotely exploitable.
Vulnerability in the Oracle VM VirtualBox product of Oracle Virtualization (component: Core). Rated low severity (CVSS 2.3), this vulnerability is low attack complexity.
Vulnerability in the MySQL Connectors product of Oracle MySQL (component: Connector/ODBC). Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Security: Encryption). Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Oracle Outside In Technology product of Oracle Fusion Middleware (component: Outside In Filters). Rated high severity (CVSS 7.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology product of Oracle Fusion Middleware (component: Outside In Filters). Rated high severity (CVSS 7.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Outside In Technology product of Oracle Fusion Middleware (component: Outside In Filters). Rated high severity (CVSS 7.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Vulnerability in the Oracle Solaris product of Oracle Systems (component: Filesystem). Rated medium severity (CVSS 5.3).
"" In X.Org X Server 1.20.4, there is a stack-based buffer overflow in the function XQueryKeymap. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. Public exploit code available and no vendor patch available.
The csv-parse module before 4.4.6 for Node.js is vulnerable to Regular Expression Denial of Service. 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.
A memory error in the function SSL_accept in nostromo nhttpd through 1.9.6 allows an attacker to trigger a denial of service via a crafted HTTP request. 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.
idreamsoft iCMS 7.0.15 allows remote attackers to cause a denial of service (resource consumption) via a query for many comments, as demonstrated by the admincp.php?app=comment&perpage= substring. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In FFmpeg before 4.2, avcodec_open2 in libavcodec/utils.c allows a NULL pointer dereference and possibly unspecified other impact when there is no valid close function pointer. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
An issue was discovered on Belkin Wemo Switch 28B WW_2.00.11057.PVT-OWRT-SNS devices. 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.
Hydra through 0.1.8 has a NULL pointer dereference and daemon crash when processing POST requests that lack a Content-Length header. 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.
A potential security vulnerability has been identified with Samsung Laser Printers. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Memory corruption in system firmware for Intel(R) NUC may allow a privileged user to potentially enable escalation of privilege, denial of service and/or information disclosure via local access. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
Pointer corruption in system firmware for Intel(R) NUC may allow a privileged user to potentially enable escalation of privilege, denial of service and/or information disclosure via local access. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
A vulnerability has been found in the implementation of the Label Distribution Protocol (LDP) protocol in EOS. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Bento4 1.5.1.0 has a NULL pointer dereference in AP4_Descriptor::GetTag in Core/Ap4Descriptor.h, related to AP4_StsdAtom::GetSampleDescription in Core/Ap4StsdAtom.cpp, as demonstrated by mp4info. 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.
Bento4 1.5.1.0 has a NULL pointer dereference in AP4_DescriptorListWriter::Action in Core/Ap4Descriptor.h, related to AP4_IodsAtom::WriteFields in Core/Ap4IodsAtom.cpp, as demonstrated by mp4encrypt. 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.
Bento4 1.5.1.0 has a NULL pointer dereference in AP4_DescriptorListInspector::Action in Core/Ap4Descriptor.h, related to AP4_IodsAtom::InspectFields in Core/Ap4IodsAtom.cpp, as demonstrated by. 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.
find_abstract_instance in dwarf2.c in the Binary File Descriptor (BFD) library (aka libbfd), as distributed in GNU Binutils 2.32, allows remote attackers to cause a denial of service (infinite. 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 denial of service vulnerability exists when Windows improperly handles objects in memory, aka 'Windows Denial of Service Vulnerability'. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
A denial of service vulnerability exists when Windows improperly handles objects in memory, aka 'Windows Denial of Service Vulnerability'. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
A denial of service vulnerability exists when Windows improperly handles objects in memory, aka 'Windows Denial of Service Vulnerability'. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
An elevation of privilege vulnerability exists when Windows Error Reporting manager improperly handles a process crash, aka 'Windows Error Reporting Manager Elevation of Privilege Vulnerability'. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
A denial of service vulnerability exists in Remote Desktop Protocol (RDP) when an attacker connects to the target system using RDP and sends specially crafted requests, aka 'Windows Remote Desktop. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
A denial of service vulnerability exists when Windows improperly handles hard links, aka 'Microsoft Windows Denial of Service Vulnerability'. Rated high severity (CVSS 7.3), this vulnerability is low attack complexity.
Affected devices improperly handle large amounts of specially crafted UDP packets. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An attacker with network access to an affected product may cause a denial of service condition by breaking the real-time synchronization (IRT) of the affected installation. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
NVIDIA Shield TV Experience prior to v8.0.1, NVIDIA Tegra software contains a vulnerability in the bootloader, where it does not validate the fields of the boot image, which may lead to code. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
NVIDIA Shield TV Experience prior to v8.0.1, NVIDIA Tegra bootloader contains a vulnerability where the software performs an incorrect bounds check, which may lead to buffer overflow resulting in. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
tinylcy Vino through 2017-12-15 allows remote attackers to cause a denial of service ("vn_get_string error: Resource temporarily unavailable" error and daemon crash) via a long URL. 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.
An exploitable Use After Free vulnerability exists in the CharProcs parsing functionality of NitroPDF. 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 vulnerability in the srxpfe process on Protocol Independent Multicast (PIM) enabled SRX series devices may lead to crash of the srxpfe process and an FPC reboot while processing (PIM) messages. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The SRX flowd process, responsible for packet forwarding, may crash and restart when processing specific multicast packets. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Receipt of a specific link-local IPv6 packet destined to the RE may cause the system to crash and restart (vmcore). Rated medium severity (CVSS 6.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An unexpected status return value weakness in the Next-Generation Multicast VPN (NG-mVPN) service of Juniper Networks Junos OS allows attacker to cause a Denial of Service (DoS) condition and core. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
On MX Series, when the SIP ALG is enabled, receipt of a certain malformed SIP packet may crash the MS-PIC component on MS-MIC or MS-MPC. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
On SRX5000 Series devices, if 'set security zones security-zone <zone> tcp-rst' is configured, the flowd process may crash when a specific TCP packet is received by the device and triggers a new. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
When an MX Series Broadband Remote Access Server (BRAS) is configured as a Broadband Network Gateway (BNG) with DHCPv6 enabled, jdhcpd might crash when receiving a specific crafted DHCP response. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The flowd process, responsible for forwarding traffic in SRX Series services gateways, may crash and restart when processing specific transit IP packets through an IPSec tunnel. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A memory leak vulnerability in the of Juniper Networks Junos OS allows an attacker to cause a Denial of Service (DoS) to the device by sending specific commands from a peered BGP host and having. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
This issue only affects devices with three (3) or more MPC10's installed in a single chassis with OSPF enabled and configured on the device. 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 SIP ALG packet processing service of Juniper Networks Junos OS allows an attacker to cause a Denial of Service (DoS) to the device by sending specific types of valid SIP. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
SSL-Proxy feature on SRX devices fails to handle a hardware resource limitation which can be exploited by remote SSL/TLS servers to crash the flowd daemon. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Under certain heavy traffic conditions srxpfe process can crash and result in a denial of service condition for the SRX1500 device. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A race condition which may occur when discarding malformed packets can result in BIND exiting due to a REQUIRE assertion failure in dispatch.c. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
An error in the EDNS Client Subnet (ECS) feature for recursive resolvers can cause BIND to exit with an assertion failure when processing a response that has malformed RRSIGs. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In BIND Supported Preview Edition, an error in the nxdomain-redirect feature can occur in versions which support EDNS Client Subnet (ECS) features. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A programming error in the nxdomain-redirect feature can cause an assertion failure in query.c if the alternate namespace used by nxdomain-redirect is a descendant of a zone that is served locally. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the headers stays below a maximum limit. 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.
In LibTomCrypt through 1.18.2, the der_decode_utf8_string function (in der_decode_utf8_string.c) does not properly detect certain invalid UTF-8 sequences. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
The ASN.1 parser in Bouncy Castle Crypto (aka BC Java) 1.63 can trigger a large attempted memory allocation, and resultant OutOfMemoryError error, via crafted ASN.1 data. 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.
An issue was discovered in Xen through 4.12.x allowing Arm domU attackers to cause a denial of service (infinite loop) involving a LoadExcl or StoreExcl operation. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
An issue was discovered in Xen through 4.11.x allowing x86 PV guest OS users to cause a denial of service because of an incompatibility between Process Context Identifiers (PCID) and shadow-pagetable. Rated medium severity (CVSS 6.5), this vulnerability is low attack complexity.
An issue was discovered in Xen through 4.11.x allowing x86 PV guest OS users to cause a denial of service or gain privileges because a guest can manipulate its virtualised %cr4 in a way that is. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
An issue was discovered in Xen through 4.11.x allowing x86 PV guest OS users to cause a denial of service or gain privileges because of an incompatibility between Process Context Identifiers (PCID). Rated high severity (CVSS 8.8), this vulnerability is low attack complexity.
An issue was discovered in Xen 4.8.x through 4.11.x allowing x86 PV guest OS users to cause a denial of service because mishandling of failed IOMMU operations causes a bug check during the cleanup of. Rated medium severity (CVSS 6.5), this vulnerability is low attack complexity. No vendor patch available.