{"id":"CVE-2026-64531","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: reject oversized nested action attrs\n\nOpen vSwitch stores generated flow actions as nlattrs, whose nla_len\nfield is u16","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: reject oversized nested action attrs\n\nOpen vSwitch stores generated flow actions as nlattrs, whose nla_len\nfield is u16. Commit a1e64addf3ff (\"net: op…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","published":"2026-07-27","updated":"2026-08-01","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-64531","references":[{"url":"https://git.kernel.org/stable/c/1b41cbe05b184f8861712f0806cc0c4f5d8c6dfe","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/3f1f755366687d051174739fb99f7d560202f60b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ab855641241387db062a5e41d9ad6b8561542572","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c66bd2626c2764f23764ff0f8277f44a9cfe8349","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d573250d228401f707f4dbc09d11227a6215ee5f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/dbd14f736be02cfe73049bd801af89becd1a0749","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f1efff8858403191361a01269c6fe8dd7f55a385","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"http://www.openwall.com/lists/oss-security/2026/07/28/8","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://www.openwall.com/lists/oss-security/2026/07/31/17","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://www.openwall.com/lists/oss-security/2026/08/01/1","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://www.openwall.com/lists/oss-security/2026/08/01/3","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd","exploit-available"],"epss":0.0038,"epssPercentile":0.31911,"ingestedAt":"2026-08-01T21:14:39.364Z","exploits":{"github":4,"githubRepos":["https://github.com/HackSpeak/CVE-2026-64531","https://github.com/mahfuzreham/OVSwrap-CVE-2026-64531-Mitigation-Tool","https://github.com/0xBlackash/CVE-2026-64531"],"checkedAt":"2026-09-24T07:53:12.017Z"},"exploitAvailable":true,"slug":"CVE-2026-64531","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: reject oversized nested action attrs\n\nOpen vSwitch stores generated flow actions as nlattrs, whose nla_len\nfield is u16. Commit a1e64addf3ff (\"net: openvswitch: remove\nmisbehaving actions length check\") allowed the total sw_flow_actions\nstream to grow beyond 64 KiB, which is valid, but also removed the last\nguard preventing a generated nested action attribute from exceeding\nU16_MAX.\n\nAn oversized generated container can thus be closed with a truncated\nnla_len. A later dump or teardown then walks a structurally different\nstream than the one that was validated. In particular, an oversized\nnested CLONE/CT action may cause subsequent bytes in the generated\nstream to be interpreted as independent actions.\n\nKeep the larger total-action-stream behavior, but make nested action\nclose reject generated containers that do not fit in nla_len, and return\nthe error through all callers. For recursive SAMPLE, CLONE, DEC_TTL, and\nCHECK_PKT_LEN builders, trim resource-owning action-list tails in reverse\nconstruction order before discarding failed wrappers, so resources copied\ninto the rejected tails are released before the wrappers are removed.\n\nMost failed outer wrappers are discarded by truncating actions_len after\nchild resources have been released. CHECK_PKT_LEN also trims its parent\nafter branch resources are gone. SET/TUNNEL close failures unwind their\nknown tun_dst ownership directly, and SET_TO_MASKED has no external\nownership and truncates on close failure.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":55,"depthScoreParts":{"impact":42.9,"likelihood":0.1,"exploitation":12,"ransomware":0},"changes":[{"seq":5396,"id":"CVE-2026-64531","ts":1788887280016,"field":"exploit_available","old":"false","new":"true"},{"seq":4279,"id":"CVE-2026-64531","ts":1788886394041,"field":"exploit_available","old":"true","new":"false"},{"seq":3028,"id":"CVE-2026-64531","ts":1788883057673,"field":"exploit_available","old":"false","new":"true"},{"seq":2057,"id":"CVE-2026-64531","ts":1788882462142,"field":"exploit_available","old":"true","new":"false"},{"seq":1130,"id":"CVE-2026-64531","ts":1788881899145,"field":"exploit_available","old":"false","new":"true"}]}