{"id":"CVE-2025-21786","state":"PUBLISHED","title":"workqueue: Put the pwq after detaching the rescuer from the pool","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nworkqueue: Put the pwq after detaching the rescuer from the pool\n\nThe commit 68f83057b913(\"workqueue: Reap workers via kthread_stop() and\nremove detach_completion\") adds code to reap the normal workers but\nmistakenly does not handle the rescuer and also removes the code waiting\nfor the rescuer in put_unbound_pool(), which caused a use-after-free bug\nreported by Cheung Wall.\n\nTo avoid the use-after-free bug, the pool’s reference must be held until\nthe detachment is complete. Therefore, move the code that puts the pwq\nafter detaching the rescuer from the pool.","publishedAt":"2025-02-27T02:18:26.406Z","updatedAt":"2026-08-05T11:54:24.903Z","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":"68f83057b913467a999e1bf9e0da6a119668f769","status":"affected","lessThan":"e7c16028a424dd35be1064a68fa318be4359310f","versionType":"git"},{"version":"68f83057b913467a999e1bf9e0da6a119668f769","status":"affected","lessThan":"835b69c868f53f959d4986bbecd561ba6f38e492","versionType":"git"},{"version":"68f83057b913467a999e1bf9e0da6a119668f769","status":"affected","lessThan":"e76946110137703c16423baf6ee177b751a34b7e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/workqueue.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.11","versionType":"semver"},{"version":"6.12.16","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.13.4","status":"unaffected","lessThanOrEqual":"6.13.*","versionType":"semver"},{"version":"6.14","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/workqueue.c"]}],"references":["https://git.kernel.org/stable/c/e7c16028a424dd35be1064a68fa318be4359310f","https://git.kernel.org/stable/c/835b69c868f53f959d4986bbecd561ba6f38e492","https://git.kernel.org/stable/c/e76946110137703c16423baf6ee177b751a34b7e"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:08:39.238Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/21xxx/CVE-2025-21786.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-21786","state":"PUBLISHED","datePublished":"2025-02-27T02:18:26.406Z","dateUpdated":"2026-08-05T11:54:24.903Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-12-29T08:45:45.765Z"},"containers":{"cna":{"title":"workqueue: Put the pwq after detaching the rescuer from the pool","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nworkqueue: Put the pwq after detaching the rescuer from the pool\n\nThe commit 68f83057b913(\"workqueue: Reap workers via kthread_stop() and\nremove detach_completion\") adds code to reap the normal workers but\nmistakenly does not handle the rescuer and also removes the code waiting\nfor the rescuer in put_unbound_pool(), which caused a use-after-free bug\nreported by Cheung Wall.\n\nTo avoid the use-after-free bug, the pool’s reference must be held until\nthe detachment is complete. Therefore, move the code that puts the pwq\nafter detaching the rescuer from the pool."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"68f83057b913467a999e1bf9e0da6a119668f769","status":"affected","lessThan":"e7c16028a424dd35be1064a68fa318be4359310f","versionType":"git"},{"version":"68f83057b913467a999e1bf9e0da6a119668f769","status":"affected","lessThan":"835b69c868f53f959d4986bbecd561ba6f38e492","versionType":"git"},{"version":"68f83057b913467a999e1bf9e0da6a119668f769","status":"affected","lessThan":"e76946110137703c16423baf6ee177b751a34b7e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/workqueue.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.11","versionType":"semver"},{"version":"6.12.16","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.13.4","status":"unaffected","lessThanOrEqual":"6.13.*","versionType":"semver"},{"version":"6.14","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/workqueue.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e7c16028a424dd35be1064a68fa318be4359310f"},{"url":"https://git.kernel.org/stable/c/835b69c868f53f959d4986bbecd561ba6f38e492"},{"url":"https://git.kernel.org/stable/c/e76946110137703c16423baf6ee177b751a34b7e"}],"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 vulnerability is in the core workqueue rescuer path and is reached by generating local workqueue load and memory pressure; there is no remote input path into `rescuer_thread()`. Exploitation requires the attacker to be executing code on the system.\nAC:L - The attacker fully controls the side of the race that matters — sustained memory pressure plus queued work on an unbound `WQ_MEM_RECLAIM` workqueue drives `pool_mayday_timeout()`/`send_mayday()` at will and can be looped indefinitely, so the narrow window between `put_pwq()` and `worker_detach_from_pool()` can be retried unboundedly until the RCU free lands first.\nPR:L - Any unprivileged local user can create the required conditions — allocating memory to stall `create_worker()` and issuing filesystem/block/network I/O that queues work on unbound `WQ_MEM_RECLAIM` workqueues (ext4-rsv-conversion, xfs, nfsiod, rpciod, scsi hosts). No capability check guards the rescuer path.\nUI:N - The rescuer is summoned automatically by the workqueue watchdog timer under memory pressure; no action by any other user or administrator-victim is needed to complete the attack.\nS:U - The freed object and the corruption both live in kernel heap memory within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - The freed `struct worker_pool` is read after free (`pool->flags`, `worker->node` list pointers) and comes from a generic kmalloc cache, so a reallocated victim object leaks its contents through the rescuer's list manipulation, giving a path to arbitrary kernel memory disclosure.\nI:H - `detach_worker()`'s `list_del(&worker->node)` performs a write-after-free of kernel pointers at the fixed offset of `pool->workers` into the freed slab object, which after heap spraying yields a controlled-offset write primitive usable for control-flow hijack and privilege escalation.\nA:H - Use-after-free on the worker pool corrupts the attached-workers list and typically produces an immediate oops/panic (KASAN reported it as a UAF), permanently wedging or crashing the kernel."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T11:54:24.903Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.12.16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.13.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.11","versionEndExcluding":"6.14"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":7.8,"attackVector":"LOCAL","baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","integrityImpact":"HIGH","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"HIGH"}},{"other":{"type":"ssvc","content":{"id":"CVE-2025-21786","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2025-02-27T18:14:15.335144Z"}}}],"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":"2025-02-27T18:22:29.313Z"}}]}}}