{"id":"CVE-2026-23413","state":"PUBLISHED","title":"clsact: Fix use-after-free in init/destroy rollback asymmetry","description":"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 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.","publishedAt":"2026-04-02T11:40:54.384Z","updatedAt":"2026-10-19T18:35:42.855Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"230bb13650b0f186f540500fd5f5f7096a822a2a","status":"affected","lessThan":"a73d95b57bf9faebdfed591bcb7ed9292062a84c","versionType":"git"},{"version":"1cb6f0bae50441f4b4b32a28315853b279c7404e","status":"affected","lessThan":"37bef86e5428d59f70a4da82b80f9a8f252fecbe","versionType":"git"},{"version":"1cb6f0bae50441f4b4b32a28315853b279c7404e","status":"affected","lessThan":"4c9af67f99aa3e51b522c54968ab3ac8272be41c","versionType":"git"},{"version":"1cb6f0bae50441f4b4b32a28315853b279c7404e","status":"affected","lessThan":"0509b762bc5e8ea7b8391130730c6d8502fc6e69","versionType":"git"},{"version":"1cb6f0bae50441f4b4b32a28315853b279c7404e","status":"affected","lessThan":"a0671125d4f55e1e98d9bde8a0b671941987e208","versionType":"git"},{"version":"f61ecf1bd5b562ebfd7d430ccb31619857e80857","status":"affected","versionType":"git"},{"version":"6.6.41","status":"affected","lessThan":"6.6.130","versionType":"semver"},{"version":"6.9.10","status":"affected","lessThan":"6.10","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/sch_generic.h","net/sched/sch_ingress.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.10","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/sch_generic.h","net/sched/sch_ingress.c"]}],"references":["https://git.kernel.org/stable/c/a73d95b57bf9faebdfed591bcb7ed9292062a84c","https://git.kernel.org/stable/c/37bef86e5428d59f70a4da82b80f9a8f252fecbe","https://git.kernel.org/stable/c/4c9af67f99aa3e51b522c54968ab3ac8272be41c","https://git.kernel.org/stable/c/0509b762bc5e8ea7b8391130730c6d8502fc6e69","https://git.kernel.org/stable/c/a0671125d4f55e1e98d9bde8a0b671941987e208"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/23xxx/CVE-2026-23413.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23413","state":"PUBLISHED","datePublished":"2026-04-02T11:40:54.384Z","dateUpdated":"2026-10-19T18:35:42.855Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-01-13T15:37:46.014Z"},"containers":{"cna":{"title":"clsact: Fix use-after-free in init/destroy rollback asymmetry","descriptions":[{"lang":"en","value":"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 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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"230bb13650b0f186f540500fd5f5f7096a822a2a","status":"affected","lessThan":"a73d95b57bf9faebdfed591bcb7ed9292062a84c","versionType":"git"},{"version":"1cb6f0bae50441f4b4b32a28315853b279c7404e","status":"affected","lessThan":"37bef86e5428d59f70a4da82b80f9a8f252fecbe","versionType":"git"},{"version":"1cb6f0bae50441f4b4b32a28315853b279c7404e","status":"affected","lessThan":"4c9af67f99aa3e51b522c54968ab3ac8272be41c","versionType":"git"},{"version":"1cb6f0bae50441f4b4b32a28315853b279c7404e","status":"affected","lessThan":"0509b762bc5e8ea7b8391130730c6d8502fc6e69","versionType":"git"},{"version":"1cb6f0bae50441f4b4b32a28315853b279c7404e","status":"affected","lessThan":"a0671125d4f55e1e98d9bde8a0b671941987e208","versionType":"git"},{"version":"f61ecf1bd5b562ebfd7d430ccb31619857e80857","status":"affected","versionType":"git"},{"version":"6.6.41","status":"affected","lessThan":"6.6.130","versionType":"semver"},{"version":"6.9.10","status":"affected","lessThan":"6.10","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/sch_generic.h","net/sched/sch_ingress.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.10","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/sch_generic.h","net/sched/sch_ingress.c"]}],"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"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable `clsact` qdisc init/destroy path is reached through local rtnetlink `RTM_NEWQDISC` traffic, not by remote packets directly.\nAC:L - The failure path is attacker-controlled by creating/replacing `clsact` with shared block indexes so `tcf_block_get_ext()` fails during rollback; no uncontrollable race is required.\nPR:L - `RTM_NEWQDISC` requires `CAP_NET_ADMIN` in the target network namespace, and `tc`/qdisc operations are reachable by an unprivileged user via user+network namespaces.\nUI:N - After local access, exploitation only requires issuing crafted netlink/qdisc operations and does not require victim interaction.\nS:U - The bug is a standard kernel memory corruption issue within the same kernel security authority, not a VM or hardware isolation boundary escape.\nC:H - The bug is a use-after-free of `tcx_entry` state reachable through old `clsact` miniq callbacks, and UAF memory reuse can provide kernel memory disclosure primitives.\nI:H - The stale miniq pointer can lead to writes through freed/reallocated kernel memory, making control-flow or kernel data corruption defensible.\nA:H - The same UAF can be triggered into kernel crashes/oopses during qdisc/filter cleanup or callback paths, causing high availability impact."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:21:33.571Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.41","versionEndExcluding":"6.6.130"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.12.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.18.20"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.19.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"7.0"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9.10"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-23413","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:07:46.676905Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","lang":"en","type":"CWE","description":"CWE-416 Use After Free"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T18:35:42.855Z"}}]}}}