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 (40217)
Clustered Data ONTAP versions 9.7 through 9.7P7 are susceptible to a vulnerability which allows an attacker with access to an intercluster LIF to cause 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.
All versions of package trim are vulnerable to Regular Expression Denial of Service (ReDoS) via trim(). 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 out-of-bounds read in the JavaScript Interpreter in Facebook Hermes prior to commit 8cb935cd3b2321c46aa6b7ed8454d95c75a7fca0 allows attackers to cause a denial of service attack or possible. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
A Denial of Service condition in Motion-Project Motion 3.2 through 4.3.1 allows remote unauthenticated users to cause a webu.c segmentation fault and kill the main process 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.
Arista’s CloudVision eXchange (CVX) server before 4.21.12M, 4.22.x before 4.22.7M, 4.23.x before 4.23.5M, and 4.24.x before 4.24.2F allows remote attackers to cause a denial of service (crash and. 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.
NVIDIA GeForce Experience, all versions prior to 3.20.5.70, contains a vulnerability in the ShadowPlay component which may lead to local privilege escalation, code execution, denial of service or. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
NVIDIA GeForce Experience, all versions prior to 3.20.5.70, contains a vulnerability in its services in which a folder is created by nvcontainer.exe under normal user login with LOCAL_SYSTEM. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
NVIDIA GeForce Experience, all versions prior to 3.20.5.70, contains a vulnerability in NVIDIA Web Helper NodeJS Web Server in which an uncontrolled search path is used to load a node module, which. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity.
CryptoPro CSP through 5.0.0.10004 on 64-bit platforms allows local users with the SeChangeNotifyPrivilege right to cause denial of service because user-mode input is mishandled during process. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. Public exploit code available and no vendor patch available.
An issue was discovered in the Linux kernel through 5.9.1, as used with Xen through 4.14.x. Rated medium severity (CVSS 4.7).
An issue was discovered in the Linux kernel through 5.9.1, as used with Xen through 4.14.x. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
An issue was discovered in Xen through 4.14.x allowing x86 guest OS users to cause a host OS denial of service, achieve data corruption, or possibly gain privileges by exploiting a race condition. Rated high severity (CVSS 7.0).
An issue was discovered in Xen through 4.14.x allowing x86 HVM and PVH guest OS users to cause a denial of service (data corruption), cause a data leak, or possibly gain privileges because coalescing. Rated high severity (CVSS 7.8).
An issue was discovered in Xen through 4.14.x allowing x86 guest OS users to cause a denial of service (data corruption), cause a data leak, or possibly gain privileges because an AMD IOMMU. Rated high severity (CVSS 7.8).
When multiple WASM threads had a reference to a module, and were looking up exported functions, one WASM thread could have overwritten another's entry in a shared stub table, resulting in a. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A logic issue was addressed with improved state management. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A buffer overflow was addressed with improved bounds checking. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
ImageMagick 7.0.10-34 allows Division by Zero in OptimizeLayerFrames in MagickCore/layer.c, which may cause a denial of service. Rated low severity (CVSS 3.3), this vulnerability is no authentication required, low attack complexity.
receive.c in fastd before v21 allows denial of service (assertion failure) when receiving packets with an invalid type code. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Adobe InDesign version 15.1.2 (and earlier) is affected by a NULL pointer dereference bug that occurs when handling a malformed .indd file. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Arista EOS before 4.21.12M, 4.22.x before 4.22.7M, 4.23.x before 4.23.5M, and 4.24.x before 4.24.2F allows remote attackers to cause a denial of service (restart of agents) by crafting a malformed. 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 ingress packet processing path of Cisco Firepower Threat Defense (FTD) Software for interfaces that are configured either as Inline Pair or in Passive mode could allow an. Rated high severity (CVSS 7.4), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
A vulnerability in the SSL/TLS session handler of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to. 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 ICMP ingress packet processing of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 4110 appliances could allow an unauthenticated, remote attacker to cause a. 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 packet processing functionality of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on. 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 SSL/TLS inspection of Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 2100 Series firewalls could allow an unauthenticated, remote attacker to cause a denial. 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 host input API daemon of Cisco Firepower Management Center (FMC) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability in the SIP inspection process of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to. 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 TCP packet processing of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to. 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 Simple Network Management Protocol (SNMP) input packet processor of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an. 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 SSL VPN negotiation process for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote. 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 OSPF Version 2 (OSPFv2) implementation of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated,. 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 licensing service of Cisco Firepower Management Center (FMC) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.The. 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 web services interface of Cisco Adaptive Security Appliance (ASA) and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to upload. 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 IP fragment-handling implementation of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote. 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 ssl_inspection component of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to crash Snort instances. 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 web interface of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an. Rated high severity (CVSS 8.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
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. No vendor patch available.
Vulnerability in the Oracle VM VirtualBox product of Oracle Virtualization (component: Core). Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
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. No vendor patch available.
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. No vendor patch available.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Logging). Rated medium severity (CVSS 4.4), this vulnerability is remotely exploitable. No vendor patch available.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: X Plugin). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Security: LDAP Auth). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
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. No vendor patch available.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: DDL). Rated medium severity (CVSS 4.4), this vulnerability is remotely exploitable. No vendor patch available.
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. No vendor patch available.
Vulnerability in the MySQL Cluster product of Oracle MySQL (component: Cluster: NDBCluster Plugin). Rated medium severity (CVSS 4.6), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Charsets). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
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. No vendor patch available.
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 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 4.9), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Oracle Business Intelligence Enterprise Edition product of Oracle Fusion Middleware (component: Analytics Actions). Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, no authentication required, 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: Optimizer). Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
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. No vendor patch available.
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. No vendor patch available.
Vulnerability in the Oracle Financial Services Analytical Applications Infrastructure product of Oracle Financial Services Applications (component: Infrastructure). Rated high severity (CVSS 8.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
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. No vendor patch available.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: DML). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Locking). Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
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. No vendor patch available.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: FTS). 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 6.5), 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 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: InnoDB). Rated low severity (CVSS 2.2), this vulnerability is remotely exploitable.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: PS). 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: FTS). 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 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 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. No vendor patch available.
Vulnerability in the PeopleSoft Enterprise HCM Global Payroll Core product of Oracle PeopleSoft (component: Security). Rated medium severity (CVSS 6.3), 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: 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: InnoDB). Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Oracle CRM Technical Foundation product of Oracle E-Business Suite (component: Preferences). Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, 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: Security: LDAP Auth). Rated low severity (CVSS 2.2), this vulnerability is remotely exploitable.
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 Hyperion Analytic Provider Services product of Oracle Hyperion (component: Smart View Provider). Rated medium severity (CVSS 4.3).
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: FTS). Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Rated medium severity (CVSS 5.5), this vulnerability is remotely exploitable, low attack complexity.
Vulnerability in the Oracle Solaris product of Oracle Systems (component: Kernel). Rated medium severity (CVSS 5.6), this vulnerability is low attack complexity.
Vulnerability in the Oracle Solaris product of Oracle Systems (component: Filesystem). Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
Vulnerability in the Database Filesystem component of Oracle Database Server. Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity.