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 (40244)
The hi3660_stub_clk_probe function in drivers/clk/hisilicon/clk-hi3660-stub.c in the Linux kernel before 4.16 allows local users to cause a denial of service (NULL pointer dereference) by triggering. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
windrvr1260.sys in Jungo DriverWizard WinDriver 12.6.0 allows attackers to cause a denial of service (BSOD) via a 0x953827bf DeviceIoControl call. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. Public exploit code available and no vendor patch available.
windrvr1260.sys in Jungo DriverWizard WinDriver 12.6.0 allows attackers to cause a denial of service (BSOD) via a 0x953826DB DeviceIoControl call. 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 Botan 1.11.32 through 2.x before 2.6.0. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A denial of service vulnerability exists in the way that Windows handles objects in memory, aka "Microsoft Graphics Component Denial of Service Vulnerability." This affects Windows 7, Windows Server. Rated medium severity (CVSS 5.5), 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 medium severity (CVSS 5.3), this vulnerability is remotely exploitable.
A denial of service vulnerability exists in the way that Windows SNMP Service handles malformed SNMP traps, aka "Windows SNMP Service Denial of Service Vulnerability." This affects Windows 7, Windows. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable.
A denial of service vulnerability exists in the HTTP 2.0 protocol stack (HTTP.sys) when HTTP.sys improperly parses specially crafted HTTP 2.0 requests, aka "HTTP.sys Denial of Service Vulnerability.". Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
A Junos device with VPLS routing-instances configured on one or more interfaces may be susceptible to an mbuf leak when processing a specific MPLS packet. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Junos OS may be impacted by the receipt of a malformed BGP UPDATE which can lead to a routing process daemon (rpd) crash and restart. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability in Junos OS SNMP MIB-II subagent daemon (mib2d) may allow a remote network based attacker to cause the mib2d process to crash resulting in a denial of service condition (DoS) for the. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required.
A vulnerability in the Network Address Translation - Protocol Translation (NAT-PT) feature of Junos OS on SRX series devices may allow a certain valid IPv6 packet to crash the flowd daemon. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
drivers/scsi/libsas/sas_scsi_host.c in the Linux kernel before 4.16 allows local users to cause a denial of service (ata qc leak) by triggering certain failure conditions. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
In Android before security patch level 2018-04-05 on Qualcomm Snapdragon Mobile and Snapdragon Wear MDM9206, MDM9607, MDM9635M, MDM9640, MDM9645, MDM9650, MDM9655, MSM8909W, SD 210/SD 212/SD 205, SD. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In Android before security patch level 2018-04-05 on Qualcomm Snapdragon Mobile and Snapdragon Wear MSM8909W, SD 210/SD 212/SD 205, SD 450, SD 615/16/SD 415, SD 625, SD 650/52, SD 820, SD 835, SD. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
soundlib/Snd_fx.cpp in OpenMPT before 1.27.07.00 and libopenmpt before 0.3.8 allows remote attackers to cause a denial of service (out-of-bounds read) via an IT or MO3 file with many nested pattern. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
The decode_init function in libavcodec/utvideodec.c in FFmpeg through 3.4.2 allows remote attackers to cause a denial of service (out of array read) via an AVI file. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
libqpdf.a in QPDF through 8.0.2 mishandles certain "expected dictionary key but found non-name object" cases, allowing remote attackers to cause a denial of service (stack exhaustion), related to the. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
The export function in libavfilter/vf_signature.c in FFmpeg through 3.4.2 allows remote attackers to cause a denial of service (out-of-array access) or possibly have unspecified other impact via a. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The caml_ba_deserialize function in byterun/bigarray.c in the standard library in OCaml 4.06.0 has an integer overflow which, in situations where marshalled data is accepted from an untrusted source,. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A cross-site request forgery vulnerability exists in Jenkins vSphere Plugin 2.16 and older in Clone.java, CloudSelectorParameter.java, ConvertToTemplate.java, ConvertToVm.java, Delete.java,. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An improper authorization vulnerability exists in Jenkins vSphere Plugin 2.16 and older in Clone.java, CloudSelectorParameter.java, ConvertToTemplate.java, ConvertToVm.java, Delete.java,. Rated medium severity (CVSS 6.3), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
In Exiv2 0.26, a divide by zero in BigTiffImage::printIFD in bigtiffimage.cpp could result in denial of service. 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.
In Exiv2 0.26, an assertion failure in BigTiffImage::readData in bigtiffimage.cpp results in an abort. 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.
In FreeBSD before 11.1-STABLE, 11.1-RELEASE-p9, 10.4-STABLE, 10.4-RELEASE-p8 and 10.3-RELEASE-p28, the length field of the ipsec option header does not count the size of the option header itself,. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In Wireshark 2.4.0 to 2.4.5 and 2.2.0 to 2.2.13, the Kerberos dissector could crash. 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.
In Wireshark 2.4.0 to 2.4.5 and 2.2.0 to 2.2.13, the VLAN dissector could crash. 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.
In Wireshark 2.4.0 to 2.4.5 and 2.2.0 to 2.2.13, the IEEE 802.15.4 dissector could crash. 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.
In Wireshark 2.4.0 to 2.4.5 and 2.2.0 to 2.2.13, the MP4 dissector could crash. 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.
In Wireshark 2.4.0 to 2.4.5, the TCP dissector could crash. 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.
In Wireshark 2.4.0 to 2.4.5, the CQL dissector could go into an infinite loop. 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.
In Wireshark 2.4.0 to 2.4.5 and 2.2.0 to 2.2.13, the LWAPP dissector could crash. 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.
JasPer 2.0.14 allows denial of service via a reachable assertion in the function jpc_abstorelstepsize in libjasper/jpc/jpc_enc.c. 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.
The xz_decomp function in xzlib.c in libxml2 2.9.8, if --with-lzma is used, allows remote attackers to cause a denial of service (infinite loop) via a crafted XML file that triggers. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and no vendor patch available.
ncmpc through 0.29 is prone to a NULL pointer dereference flaw. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In Ruby before 2.2.10, 2.3.x before 2.3.7, 2.4.x before 2.4.4, 2.5.x before 2.5.1, and 2.6.0-preview1, an attacker can pass a large HTTP request with a crafted header to WEBrick server or a crafted. 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.
The Stealth endpoint in Unisys Stealth SVG 2.8.x, 3.0.x before 3.0.1999, 3.1.x, 3.2.x before 3.2.030, and 3.3.x before 3.3.016, when running on Linux and AIX, allows remote attackers to cause a. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In Qualcomm Android for MSM, Firefox OS for MSM, and QRD Android with all Android releases from CAF using the Linux kernel before security patch level 2018-04-05, due to a race condition, a Use After. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
In Qualcomm Android for MSM, Firefox OS for MSM, and QRD Android with all Android releases from CAF using the Linux kernel before security patch level 2018-04-05, in the kernel IPA driver, a Use. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
In Qualcomm Android for MSM, Firefox OS for MSM, and QRD Android with all Android releases from CAF using the Linux kernel before security patch level 2018-04-05, while notifying a DCI client, a Use. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In Qualcomm Android for MSM, Firefox OS for MSM, and QRD Android with all Android releases from CAF using the Linux kernel before security patch level 2018-04-05, a Use After Free condition can occur. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In Qualcomm Android for MSM, Firefox OS for MSM, and QRD Android with all Android releases from CAF using the Linux kernel before security patch level 2018-04-05, untrusted pointer dereference in. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. 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 certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), 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 certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. 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 certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. Rated high severity (CVSS 8.8), 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 certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. 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 certain Apple products. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in certain Apple products. 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 certain Apple products. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
NVIDIA GPU Display Driver contains a vulnerability in the DirectX and OpenGL Usermode drivers where a specially crafted pixel shader can cause infinite recursion leading to denial of service. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
NVIDIA Windows GPU Display Driver contains a vulnerability in the kernel mode layer handler for DxgkDdiEscape where the software allows an actor access to restricted functionality that is unnecessary. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
NVIDIA Windows GPU Display Driver contains a vulnerability in the DirectX 10 Usermode driver, where a specially crafted pixel shader can cause writing to unallocated memory, leading to denial of. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
NVIDIA Windows GPU Display Driver contains a vulnerability in the kernel mode layer (nvlddmkm.sys) handler for DxgkDdiEscape where a NULL pointer dereference occurs which may lead to denial of. Rated high severity (CVSS 8.8), this vulnerability is low attack complexity. No vendor patch available.
NVIDIA GPU Display Driver contains a vulnerability in kernel mode layer handler where a NULL pointer dereference may lead to denial of service or potential escalation of privileges. Rated high severity (CVSS 8.8), this vulnerability is low attack complexity. No vendor patch available.
NVIDIA Windows GPU Display Driver contains a vulnerability in the kernel mode layer handler for DxgkDdiEscape where the software uses a sequential operation to read or write a buffer, but it uses an. Rated high severity (CVSS 8.8), this vulnerability is low attack complexity. No vendor patch available.
NVIDIA Windows GPU Display Driver contains a vulnerability in the kernel mode layer (nvlddmkm.sys) handler for DxgkDdiEscape where a NULL pointer dereference may lead to denial of service or possible. Rated high severity (CVSS 8.8), this vulnerability is low attack complexity. No vendor patch available.
The ext4_xattr_check_entries function in fs/ext4/xattr.c in the Linux kernel through 4.15.15 does not properly validate xattr sizes, which causes misinterpretation of a size as an error code, and. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
The ext4_fill_super function in fs/ext4/super.c in the Linux kernel through 4.15.15 does not always initialize the crc32c checksum driver, which allows attackers to cause a denial of service. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available.