{"id":"CVE-2026-53266","published":"2026-06-25T09:16:44Z","modified":"2026-09-19T04:17:53Z","title":"Linux Kernel Out-of-Bounds Write Vulnerability","vendor":"Linux","product":"Kernel","tier":"core","eol":null,"description":{"text":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: bridge: make ebt_snat ARP rewrite writable\n\nThe ebtables SNAT target keeps the Ethernet source address rewrite\nbehind skb_ensure_writable(skb, 0).  This is intentional: at the bridge\nebtables hooks the Ethernet header is addressed through\nskb_mac_header()/eth_hdr(), while skb->data points at the Ethernet\npayload.  Asking skb_ensure_writable() for ETH_HLEN bytes would check\nthe payload, not the Ethernet header, and would reintroduce the small\npacket regression fixed by commit 63137bc5882a.\n\nHowever, the optional ARP sender hardware address rewrite is different.\nIt writes through skb_store_bits() at an offset relative to skb->data:\n\n        skb_store_bits(skb, sizeof(struct arphdr), info->mac, ETH_ALEN)\n\nskb_header_pointer() only safely reads the ARP header; it does not make\nthe later sender hardware address range writable.  If that range is\nstill held in a nonlinear skb fragment backed by a splice-imported file\npage, skb_store_bits() maps the frag page and copies the new MAC address\ndirectly into it.\n\nEnsure the ARP SHA range is writable before reading the ARP header and\nbefore calling skb_store_bits().","provenance":"source","from":"NVD"},"summary":{"text":"The Linux kernel's netfilter bridge ebt_snat target has an out-of-bounds write flaw in its optional ARP sender hardware address rewrite, which writes through skb_store_bits() without first ensuring the target range is writable. An attacker with local access and low privileges can trigger this when the ARP sender hardware address sits in a nonlinear skb fragment backed by a splice-imported file page, causing the kernel to copy the new MAC address directly into that page, with no user interaction required.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:14:52Z"},"cvss":{"score":8.8,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.00934,"percentile":0.60731,"date":"2026-10-30","provenance":"source"},"kev":{"dateAdded":"2026-09-18","dueDate":"2026-09-21","ransomware":false,"requiredAction":"Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.","notes":"This vulnerability affects an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: ; https://git.kernel.org/stable/c/bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87; https://git.kernel.org/stable/c/76280b78cc9f23bdc6438e10ad6dff148ef8375b; https://git.kernel.org/stable/c/b7e91939ba9be805a62a257fa4e227dffbb88fa0; https://git.kernel.org/stable/c/afd64b59c3de9bbbdd3759e834fdc55cda716e0b; https://git.kernel.org/stable/c/153ea96c806aea395daba907a4f88480b6ad5093; https://git.kernel.org/stable/c/b18675263db1147c8e1cab625400c13a0d87bd2d; https://git.kernel.org/stable/c/c9b5ff59feffb92a147a84a5aa28acd2cb8ff4c5; https://git.kernel.org/stable/c/67ba971ae02514d85818fe0c32549ab4bfa3bf49 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-53266","provenance":"source"},"vulncheckKev":{"dateAdded":"2026-09-18","exploitedFirstSeen":"2026-09-18","ransomware":false,"evidence":[{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2026-09-18"}],"evidenceTotal":1,"provenance":"source"},"exploited":true,"otx":{"pulseCount":41,"pulses":[{"name":"Actively_Exploited_Kev | Oct 31, 2026","url":"https://otx.alienvault.com/pulse/6ae4aefab0c2191cecd41862","created":"2026-10-30"},{"name":"Actively_Exploited_Kev | Oct 30, 2026","url":"https://otx.alienvault.com/pulse/6ae35d889ea92b4ce19c2680","created":"2026-10-29"},{"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":"PyPI Becomes a Distribution Channel for Crimeware: The Case of 'saeka,' a Carding Automation Tool.","url":"https://otx.alienvault.com/pulse/6ad7cd3ea852b96a1ec71460","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"}],"provenance":"machine"},"cwes":[{"id":"CWE-787","name":"Out-of-bounds Write"}],"references":[{"url":"https://git.kernel.org/stable/c/153ea96c806aea395daba907a4f88480b6ad5093","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/67ba971ae02514d85818fe0c32549ab4bfa3bf49","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/76280b78cc9f23bdc6438e10ad6dff148ef8375b","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/afd64b59c3de9bbbdd3759e834fdc55cda716e0b","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/b18675263db1147c8e1cab625400c13a0d87bd2d","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/b7e91939ba9be805a62a257fa4e227dffbb88fa0","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/bf84ad7c7a9ede46e31afaa41a1ba06a159e8c87","tags":["Patch"]},{"url":"https://git.kernel.org/stable/c/c9b5ff59feffb92a147a84a5aa28acd2cb8ff4c5","tags":["Patch"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-53266","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 privilege use corrupts kernel memory via write","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"skb_store_bits() maps the frag page and copies the new MAC address","start":1010,"end":1076}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2026-39217","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-39217","exploited":true,"exploitedSince":"2026-09-18","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":1,"skipped":0,"earliest":"2026-09-20","earliestUrl":"https://github.com/suominen/CVE-2026-53266","repos":[{"name":"suominen/CVE-2026-53266","url":"https://github.com/suominen/CVE-2026-53266","stars":0,"created":"2026-09-20"}]},"first":{"date":"2026-09-20","source":"PoC-in-GitHub","url":"https://github.com/suominen/CVE-2026-53266"},"provenance":"source"},"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1068"],"provenance":"ai"}],"timeline":[{"date":"2026-06-25","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53266","provenance":"source"},{"date":"2026-09-18","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","provenance":"source"},{"date":"2026-09-18","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2026-09-18","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-39217","provenance":"source"},{"date":"2026-09-20","kind":"exploit-public","label":"First public exploit: PoC-in-GitHub","url":"https://github.com/suominen/CVE-2026-53266","provenance":"source"}],"speed":{"daysToPublicExploit":87,"firstExploitFrom":"PoC-in-GitHub","daysToKev":85},"priority":{"score":71.3,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":10.0,"detail":"added 43 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":12.15,"detail":"percentile 0.6073"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 PoC-in-GitHub repo"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"41 pulses"},{"name":"CVSS severity","points":6.16,"detail":"base score 8.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]},"lineage":{"familyId":"fam-class-linux-kernel-cwe-787"}}