{"id":"CVE-2026-23413","title":"clsact: Fix use-after-free in init/destroy rollback asymmetry","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nclsact: Fix use-after-free in init/destroy rollback asymmetry\n\nFix a use-after-free in the clsact qdisc upon init/destroy rollback asymmetry.\nThe latter is achieved by …","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","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 230bb13650b0f186f540500fd5f5f7096a822a2a < a73d95b57bf9faebdfed591bcb7ed9292062a84c","Linux >= 1cb6f0bae50441f4b4b32a28315853b279c7404e < 37bef86e5428d59f70a4da82b80f9a8f252fecbe","Linux >= 1cb6f0bae50441f4b4b32a28315853b279c7404e < 4c9af67f99aa3e51b522c54968ab3ac8272be41c","Linux >= 1cb6f0bae50441f4b4b32a28315853b279c7404e < 0509b762bc5e8ea7b8391130730c6d8502fc6e69","Linux >= 1cb6f0bae50441f4b4b32a28315853b279c7404e < a0671125d4f55e1e98d9bde8a0b671941987e208","Linux f61ecf1bd5b562ebfd7d430ccb31619857e80857","Linux >= 6.6.41 < 6.6.130","Linux >= 6.9.10 < 6.10","Linux 6.10"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:07:46.676905Z"},"published":"2026-04-02","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:09:55.294Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-23413","references":[{"url":"https://git.kernel.org/stable/c/a73d95b57bf9faebdfed591bcb7ed9292062a84c"},{"url":"https://git.kernel.org/stable/c/37bef86e5428d59f70a4da82b80f9a8f252fecbe"},{"url":"https://git.kernel.org/stable/c/4c9af67f99aa3e51b522c54968ab3ac8272be41c"},{"url":"https://git.kernel.org/stable/c/0509b762bc5e8ea7b8391130730c6d8502fc6e69"},{"url":"https://git.kernel.org/stable/c/a0671125d4f55e1e98d9bde8a0b671941987e208"}],"tags":["cve.org"],"epss":0.00119,"epssPercentile":0.01652,"ingestedAt":"2026-10-16T17:24:46.644Z","slug":"CVE-2026-23413","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nclsact: Fix use-after-free in init/destroy rollback asymmetry\n\nFix a use-after-free in the clsact qdisc upon init/destroy rollback asymmetry.\nThe latter is achieved by first fully initializing a clsact instance, and\nthen in a second step having a replacement failure for the new clsact qdisc\ninstance. clsact_init() initializes ingress first and then takes care of the\negress part. This can fail midway, for example, via tcf_block_get_ext(). Upon\nfailure, the kernel will trigger the clsact_destroy() callback.\n\nCommit 1cb6f0bae504 (\"bpf: Fix too early release of tcx_entry\") details the\nway how the transition is happening. If tcf_block_get_ext on the q->ingress_block\nends up failing, we took the tcx_miniq_inc reference count on the ingress\nside, but not yet on the egress side. clsact_destroy() tests whether the\n{ingress,egress}_entry was non-NULL. However, even in midway failure on the\nreplacement, both are in fact non-NULL with a valid egress_entry from the\nprevious clsact instance.\n\nWhat we really need to test for is whether the qdisc instance-specific ingress\nor egress side previously got initialized. This adds a small helper for checking\nthe miniq initialization called mini_qdisc_pair_inited, and utilizes that upon\nclsact_destroy() in order to fix the use-after-free scenario. Convert the\ningress_destroy() side as well so both are consistent to each other.\n\n## Affected\n\n- `Linux >= 230bb13650b0f186f540500fd5f5f7096a822a2a < a73d95b57bf9faebdfed591bcb7ed9292062a84c`\n- `Linux >= 1cb6f0bae50441f4b4b32a28315853b279c7404e < 37bef86e5428d59f70a4da82b80f9a8f252fecbe`\n- `Linux >= 1cb6f0bae50441f4b4b32a28315853b279c7404e < 4c9af67f99aa3e51b522c54968ab3ac8272be41c`\n- `Linux >= 1cb6f0bae50441f4b4b32a28315853b279c7404e < 0509b762bc5e8ea7b8391130730c6d8502fc6e69`\n- `Linux >= 1cb6f0bae50441f4b4b32a28315853b279c7404e < a0671125d4f55e1e98d9bde8a0b671941987e208`\n- `Linux f61ecf1bd5b562ebfd7d430ccb31619857e80857`\n- `Linux >= 6.6.41 < 6.6.130`\n- `Linux >= 6.9.10 < 6.10`\n- `Linux 6.10`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}