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 (40209)
An issue was discovered in swftools through 20200710. 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 sela through 20200412. 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 sela through 20200412. 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 sela through 20200412. 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 sela through 20200412. 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 pdftools through 20200714. 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 pdftools through 20200714. 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 pdftools through 20200714. 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 pdftools through 20200714. 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 pdftools through 20200714. 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 libxsmm through v1.16.1-93. 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.
An issue was discovered in libslax through v0.22.1. 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.
An issue was discovered in libredwg through v0.10.1.3751. 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.
An issue was discovered in libredwg through v0.10.1.3751. 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.
An issue was discovered in libjpeg through 2020021. 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.
An issue was discovered in libjpeg through 2020021. 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.
An issue was discovered in libjpeg through 2020021. 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.
An issue was discovered in libjpeg through 2020021. 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.
An issue was discovered in libjpeg through 2020021. 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.
An issue was discovered in libjpeg through 2020021. 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.
Integer Overflow vulnerability in function filter_sobel in libavfilter/vf_convolution.c in Ffmpeg 4.2.1, allows attackers to cause a Denial of Service or other unspecified impacts. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
Integer Overflow vulnerability in function filter_robert in libavfilter/vf_convolution.c in Ffmpeg 4.2.1, allows attackers to cause a Denial of Service or other unspecified impacts. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
Integer Overflow vulnerability in function filter_prewitt in libavfilter/vf_convolution.c in Ffmpeg 4.2.1, allows attackers to cause a Denial of Service or other unspecified impacts. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
Integer Overflow vulnerability in function filter16_sobel in libavfilter/vf_convolution.c in Ffmpeg 4.2.1, allows attackers to cause a Denial of Service or other unspecified impacts. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
Integer Overflow vulnerability in function filter16_roberts in libavfilter/vf_convolution.c in Ffmpeg 4.2.1, allows attackers to cause a Denial of Service or other unspecified impacts. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
An issue was discovered in heif through through v3.6.2. 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 gravity through 0.8.1. 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 gravity through 0.8.1. 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 gravity through 0.8.1. 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 gravity through 0.8.1. 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 fig2dev before 3.2.8.. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
An issue was discovered in faad2 through 2.10.0. 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 faust through v2.30.5. 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 gpac through 20200801. 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 gpac through 20200801. 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 segmentation fault in the redis-server component of Redis 5.0.7 leads to a denial of service (DOS). Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
RealVNC Viewer 6.21.406 allows remote VNC servers to cause a denial of service (application crash) via crafted RFB protocol data. 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.
XML Entity Expansion injection vulnerability in McAfee Endpoint Security (ENS) for Windows prior to 10.7.0 September 2021 Update allows a local user to initiate high CPU and memory consumption. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
code-server is vulnerable to Inefficient Regular Expression Complexity. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
ansi-regex is vulnerable to Inefficient Regular Expression Complexity. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
taro is vulnerable to Inefficient Regular Expression Complexity. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
nth-check is vulnerable to Inefficient Regular Expression Complexity. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
A use after free can occur due to improper validation of P2P device address in PD Request frame in Snapdragon Auto, Snapdragon Compute, Snapdragon Connectivity, Snapdragon Consumer IOT, Snapdragon. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Null pointer dereference occurs due to improper validation when the preemption feature enablement is toggled in Snapdragon Auto, Snapdragon Compute, Snapdragon Connectivity, Snapdragon Consumer IOT,. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) 11.1 and 11.5 under very specific conditions, could allow a local user to keep running a procedure that could cause the system to run. Rated medium severity (CVSS 5.1), this vulnerability is no authentication required. No vendor patch available.
Apache Tomcat 8.5.0 to 8.5.63, 9.0.0-M1 to 9.0.43 and 10.0.0-M1 to 10.0.2 did not properly validate incoming TLS packets. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Malformed requests may cause the server to dereference a NULL pointer.4.48 and earlier. 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.
semver-regex is vulnerable to Inefficient Regular Expression Complexity. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
prism is vulnerable to Inefficient Regular Expression Complexity. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
vim is vulnerable to Use After Free. Rated high severity (CVSS 7.3), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
vuelidate is vulnerable to Inefficient Regular Expression Complexity. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
Windows Installer Denial of Service Vulnerability. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
nodejs-tmpl is vulnerable to Inefficient Regular Expression Complexity. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
An invalid read in the stb_image.h component of libsixel prior to v1.8.5 allows attackers to cause a denial of service (DOS) via a crafted PSD file. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
An issue in the dither.c component of libsixel prior to v1.8.4 allows attackers to cause a denial of service (DOS) via a crafted PNG file. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
On BIG-IP version 16.0.x before 16.0.1.2, 15.1.x before 15.1.3, 14.1.x before 14.1.4, 13.1.x before 13.1.4, and 12.1.x before 12.1.6, when an HTTP profile is configured on a virtual server,. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
On version 16.x before 16.1.0, 15.1.x before 15.1.3.1, 14.1.x before 14.1.4.3, and all versions of 13.1.x, 12.1.x and 11.6.x, when BIG-IP APM performs Online Certificate Status Protocol (OCSP). Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
On version 15.1.x before 15.1.3, 14.1.x before 14.1.3.1, and 13.1.x before 13.1.3.6, when the brute force protection feature of BIG-IP Advanced WAF or BIG-IP ASM is enabled on a virtual server and. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
On BIG-IP version 16.0.x before 16.0.1.2 and 15.1.x before 15.1.3, when the iRules RESOLVER::summarize command is used on a virtual server, undisclosed requests can cause an increase in Traffic. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
SAP CommonCryptoLib version 8.5.38 or lower is vulnerable to null pointer dereference vulnerability when an unauthenticated attacker sends crafted malicious data in the HTTP requests over the. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
When a user opens manipulated files received from untrusted sources in SAP 3D Visual Enterprise Viewer version - 9, the application crashes and becomes temporarily unavailable to the user until. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability has been identified in SIMATIC CP 343-1 (incl. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Buffer Overflow vulnerability could allow attackers to corrupt memory to execute arbitrary code or crash the application.
Affected versions of Atlassian Jira Server and Data Center allow unauthenticated remote attackers to impact the application's availability via a Denial of Service (DoS) vulnerability in the. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The gf_isom_vp_config_get function in GPAC 1.0.1 allows attackers to cause a denial of service (NULL pointer dereference) via a crafted file in the MP4Box command. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
The DumpTrackInfo function in GPAC 1.0.1 allows attackers to cause a denial of service (NULL pointer dereference) via a crafted file in the MP4Box command. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
Stack buffer overflow in the hevc_parse_vps_extension function in MP4Box in GPAC 1.0.1 allows attackers to cause a denial of service or execute arbitrary code via a crafted file. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
The trak_box_size function in GPAC 1.0.1 allows attackers to cause a denial of service (NULL pointer dereference) via a crafted file in the MP4Box command. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
The abst_box_size function in GPAC 1.0.1 allows attackers to cause a denial of service (NULL pointer dereference) via a crafted file in the MP4Box command. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
Heap buffer overflow in the URL_GetProtocolType function in MP4Box in GPAC 1.0.1 allows attackers to cause a denial of service or execute arbitrary code via a crafted file. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
The gf_odf_desc_copy function in GPAC 1.0.1 allows attackers to cause a denial of service (NULL pointer dereference) via a crafted file in the MP4Box command. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
Heap buffer overflow in the print_udta function in MP4Box in GPAC 1.0.1 allows attackers to cause a denial of service or execute arbitrary code via a crafted file. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
Injection attack caused the denial of service vulnerability in NetIQ Access Manager prior to 5.0.1 and 4.5.4. Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
All versions of the afffected TOYOPUC-PC10 Series,TOYOPUC-Plus Series,TOYOPUC-PC3J/PC2J Series, TOYOPUC-Nano Series products may not be able to properly process an ICMP flood, which may allow an. Rated medium severity (CVSS 4.3), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
The rencode package through 1.0.6 for Python allows an infinite loop in typecode decoding (such as via ;\x2f\x7f), enabling a remote attack that consumes CPU and memory. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
NULL pointer dereference vulnerability in NPU driver prior to SMR Sep-2021 Release 1 allows attackers to cause memory corruption. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
NULL pointer dereference vulnerability in ION driver prior to SMR Sep-2021 Release 1 allows attackers to cause memory corruption. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
An improper input validation vulnerability in loading graph file in DSP driver prior to SMR Sep-2021 Release 1 allows attackers to perform permanent denial of service on the device. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
D-Link DSL-3782 EU v1.01:EU v1.03 is affected by a buffer overflow which can cause a denial of service. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. This Buffer Copy without Size Check vulnerability could allow attackers to overflow a buffer to corrupt adjacent memory.
In modem 2G RRM, there is a possible system crash due to a heap buffer overflow. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In modem 2G RRM, there is a possible system crash due to a heap buffer overflow. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In modem 2G RRM, there is a possible system crash due to a heap buffer overflow. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In modem 2G RRM, there is a possible system crash due to a heap buffer overflow. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The variable import endpoint was not protected by authentication in Airflow >=2.0.0, <2.1.3. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Potential null pointer dereference in KGSL GPU auxiliary command due to improper validation of user input in Snapdragon Auto, Snapdragon Connectivity, Snapdragon Industrial IOT, Snapdragon Mobile. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
Possible null pointer dereference due to race condition between timeline fence signal and time line fence destroy in Snapdragon Auto, Snapdragon Connectivity, Snapdragon Industrial IOT, Snapdragon. Rated high severity (CVSS 7.0).
Possible assertion due to lack of physical layer state validation in Snapdragon Auto, Snapdragon Compute, Snapdragon Connectivity, Snapdragon Consumer Electronics Connectivity, Snapdragon Industrial. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A race condition in fastrpc kernel driver for dynamic process creation can lead to use after free scenario in Snapdragon Auto, Snapdragon Connectivity, Snapdragon Mobile, Snapdragon Wearables. Rated medium severity (CVSS 6.4).
Null Pointer Dereference may occur due to improper validation while processing crafted SDP body in Snapdragon Auto, Snapdragon Compute, Snapdragon Connectivity, Snapdragon Consumer IOT, Snapdragon. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Possible null pointer dereference due to lack of validation check for passed pointer during key import in Snapdragon Auto, Snapdragon Compute, Snapdragon Connectivity, Snapdragon Consumer IOT,. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
UE assertion is possible due to improper validation of invite message with SDP body in Snapdragon Auto, Snapdragon Compute, Snapdragon Connectivity, Snapdragon Consumer IOT, Snapdragon Industrial. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.