{"id":"CVE-2021-22555","published":"2021-07-07T12:15:08Z","modified":"2026-10-13T18:25:34Z","title":"Linux Kernel Heap Out-of-Bounds Write Vulnerability","vendor":"Linux","product":"Kernel","tier":"core","eol":null,"description":{"text":"A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c. This allows an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space","provenance":"source","from":"NVD"},"summary":{"text":"A heap out-of-bounds write in the x_tables component (net/netfilter/x_tables.c) of the Linux kernel allows heap memory corruption that can lead to privilege escalation or denial of service. An attacker with local, low-privileged access can trigger it through a user namespace, without requiring user interaction.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:10:45Z"},"cvss":{"score":7.8,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.78684,"percentile":0.99587,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2025-10-06","dueDate":"2025-10-27","ransomware":false,"requiredAction":"Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.","notes":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21 ; https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d ; https://security.netapp.com/advisory/ntap-20210805-0010/ ; https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528 ; https://nvd.nist.gov/vuln/detail/CVE-2021-22555","provenance":"source"},"vulncheckKev":{"dateAdded":"2024-03-18","exploitedFirstSeen":"2024-03-18","ransomware":false,"evidence":[{"url":"https://www.trendmicro.com/en_us/research/24/c/earth-krahang.html","date":"2024-03-18"},{"url":"https://securelist.com/vulnerabilities-and-exploits-in-q2-2025/117333/","date":"2025-08-27"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2025-10-06"},{"url":"https://securelist.com/vulnerabilities-and-exploits-in-q3-2025/118197/","date":"2025-12-03"},{"url":"https://www.loginsoft.com/reports/annually/vulnerability-intelligence-report-2025","date":"2026-01-20"},{"url":"https://securelist.com/vulnerabilities-and-exploits-in-q4-2025/119105/","date":"2026-03-06"},{"url":"https://www.redhat.com/en/resources/product-security-risk-report-2025","date":"2026-04-10"},{"url":"https://securelist.com/vulnerabilities-and-exploits-in-q2-2026/121091/","date":"2026-08-26"}],"evidenceTotal":8,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"name":"Actively_Exploited_Kev | Oct 29, 2026","url":"https://otx.alienvault.com/pulse/6ae20c1db17e7057ae7d9ad1","created":"2026-10-28"},{"name":"Actively_Exploited_Kev | Oct 28, 2026","url":"https://otx.alienvault.com/pulse/6ae0ba7e0e2a97ff7b218819","created":"2026-10-27"},{"name":"Actively_Exploited_Kev | Oct 27, 2026","url":"https://otx.alienvault.com/pulse/6adf68b85c3e852f3c111d18","created":"2026-10-26"},{"name":"Actively_Exploited_Kev | Oct 24, 2026","url":"https://otx.alienvault.com/pulse/6adb740e397c3ad4799aa4cd","created":"2026-10-23"},{"name":"Actively_Exploited_Kev | Oct 23, 2026","url":"https://otx.alienvault.com/pulse/6ada236fcfba2dfa730ea482","created":"2026-10-22"},{"name":"Actively_Exploited_Kev | Oct 22, 2026","url":"https://otx.alienvault.com/pulse/6ad8d33a077cbb5cab524d80","created":"2026-10-21"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 20, 2026","url":"https://otx.alienvault.com/pulse/6ad62f63c24a405a3423cc13","created":"2026-10-19"},{"name":"Actively_Exploited_Kev | Oct 19, 2026","url":"https://otx.alienvault.com/pulse/6ad4dda174e5797d0bd238b7","created":"2026-10-18"},{"name":"Actively_Exploited_Kev | Oct 18, 2026","url":"https://otx.alienvault.com/pulse/6ad38c22e1848f8189d1c121","created":"2026-10-17"}],"provenance":"machine"},"cwes":[{"id":"CWE-787","name":"Out-of-bounds Write"}],"references":[{"url":"http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html","tags":["Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21","tags":["Mailing List","Patch","Vendor Advisory"]},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d","tags":["Mailing List","Patch","Vendor Advisory"]},{"url":"https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528","tags":["Exploit","Third Party Advisory"]},{"url":"https://security.netapp.com/advisory/ntap-20210805-0010/","tags":["Third Party Advisory"]},{"url":"http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html","tags":["Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21","tags":["Mailing List","Patch","Vendor Advisory"]},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d","tags":["Mailing List","Patch","Vendor Advisory"]},{"url":"https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528","tags":["Exploit","Third Party Advisory"]},{"url":"https://security.netapp.com/advisory/ntap-20210805-0010/","tags":["Third Party Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22555","tags":["US Government Resource"]}],"techniques":[{"id":"T1068","name":"Exploitation for Privilege Escalation","tactics":["privilege-escalation"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: local exploit of kernel memory corruption","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"allows an attacker to gain privileges or cause a DoS","start":110,"end":162}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1499.004","name":"Application or System Exploitation","tactics":["impact"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: heap corruption crashes kernel, denial of service","mappingType":"primary_impact","evidence":[{"from":"description","quote":"cause a DoS (via heap memory corruption)","start":151,"end":191}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-9696","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-9696","exploited":true,"exploitedSince":"2025-10-06","provenance":"source"},"exploits":[{"id":50135,"url":"https://www.exploit-db.com/exploits/50135","title":"Linux Kernel 2.6.19 < 5.9 - 'Netfilter Local Privilege Escalation","type":"local","platform":"linux","date":"2021-07-15","verified":true,"provenance":"source"}],"exploitSources":{"exploitdb":{"count":1,"earliest":"2021-07-15"},"pocGithub":{"count":9,"skipped":4,"earliest":"2021-07-15","earliestUrl":"https://github.com/JoneyJunior/cve-2021-22555","repos":[{"name":"veritas501/CVE-2021-22555-PipeVersion","url":"https://github.com/veritas501/CVE-2021-22555-PipeVersion","stars":40,"created":"2022-04-05"},{"name":"xyjl-ly/CVE-2021-22555-Exploit","url":"https://github.com/xyjl-ly/CVE-2021-22555-Exploit","stars":14,"created":"2021-07-16"},{"name":"cgwalters/container-cve-2021-22555","url":"https://github.com/cgwalters/container-cve-2021-22555","stars":4,"created":"2021-07-16"},{"name":"tukru/CVE-2021-22555","url":"https://github.com/tukru/CVE-2021-22555","stars":3,"created":"2023-08-05"},{"name":"JoneyJunior/cve-2021-22555","url":"https://github.com/JoneyJunior/cve-2021-22555","stars":1,"created":"2021-07-15"}]},"metasploit":[{"name":"Netfilter x_tables Heap OOB Write Privilege 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unknown"}]},"lineage":{"familyId":"fam-class-linux-kernel-cwe-787"}}