{"id":"CVE-2025-40047","state":"PUBLISHED","title":"io_uring/waitid: always prune wait queue entry in io_waitid_wait()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/waitid: always prune wait queue entry in io_waitid_wait()\n\nFor a successful return, always remove our entry from the wait queue\nentry list. Previously this was skipped if a cancelation was in\nprogress, but this can race with another invocation of the wait queue\nentry callback.","publishedAt":"2025-10-28T11:48:24.625Z","updatedAt":"2026-08-05T12:07:20.600Z","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":"f31ecf671ddc498f20219453395794ff2383e06b","status":"affected","lessThan":"696ba6032081e617564a8113a001b8d7943cb928","versionType":"git"},{"version":"f31ecf671ddc498f20219453395794ff2383e06b","status":"affected","lessThan":"3e2205db2f0608898d535da1964e1b376aacfdaa","versionType":"git"},{"version":"f31ecf671ddc498f20219453395794ff2383e06b","status":"affected","lessThan":"2f8229d53d984c6a05b71ac9e9583d4354e3b91f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/waitid.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.7","versionType":"semver"},{"version":"6.12.53","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.17.3","status":"unaffected","lessThanOrEqual":"6.17.*","versionType":"semver"},{"version":"6.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/waitid.c"]}],"references":["https://git.kernel.org/stable/c/696ba6032081e617564a8113a001b8d7943cb928","https://git.kernel.org/stable/c/3e2205db2f0608898d535da1964e1b376aacfdaa","https://git.kernel.org/stable/c/2f8229d53d984c6a05b71ac9e9583d4354e3b91f"],"weaknesses":[],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/40xxx/CVE-2025-40047.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-40047","state":"PUBLISHED","datePublished":"2025-10-28T11:48:24.625Z","dateUpdated":"2026-08-05T12:07:20.600Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T07:20:57.156Z"},"containers":{"cna":{"title":"io_uring/waitid: always prune wait queue entry in io_waitid_wait()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/waitid: always prune wait queue entry in io_waitid_wait()\n\nFor a successful return, always remove our entry from the wait queue\nentry list. Previously this was skipped if a cancelation was in\nprogress, but this can race with another invocation of the wait queue\nentry callback."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f31ecf671ddc498f20219453395794ff2383e06b","status":"affected","lessThan":"696ba6032081e617564a8113a001b8d7943cb928","versionType":"git"},{"version":"f31ecf671ddc498f20219453395794ff2383e06b","status":"affected","lessThan":"3e2205db2f0608898d535da1964e1b376aacfdaa","versionType":"git"},{"version":"f31ecf671ddc498f20219453395794ff2383e06b","status":"affected","lessThan":"2f8229d53d984c6a05b71ac9e9583d4354e3b91f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/waitid.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.7","versionType":"semver"},{"version":"6.12.53","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.17.3","status":"unaffected","lessThanOrEqual":"6.17.*","versionType":"semver"},{"version":"6.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/waitid.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/696ba6032081e617564a8113a001b8d7943cb928"},{"url":"https://git.kernel.org/stable/c/3e2205db2f0608898d535da1964e1b376aacfdaa"},{"url":"https://git.kernel.org/stable/c/2f8229d53d984c6a05b71ac9e9583d4354e3b91f"}],"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 reached through the io_uring syscall interface (`io_uring_setup`/`io_uring_enter` submitting an `IORING_OP_WAITID` SQE) plus process-management signals, all of which require local access to the system. Per kernel scoring guidance, io_uring bugs are Local.\nAC:L - The attacker controls both sides of the race: it drives the wait-queue wakeups at arbitrary rate by forking children and looping SIGSTOP/SIGCONT (`do_notify_parent_cldstop` → `__wake_up_parent`), while concurrently submitting `IORING_OP_ASYNC_CANCEL` or tearing down the ring from another thread to grab the competing reference. syzbot produced a working reproducer and confirmed the fix, showing the window is hit reliably.\nPR:L - Any unprivileged local user can create an io_uring ring — `sysctl_io_uring_disabled` defaults to 0 and `IORING_OP_WAITID` carries no capability check — and waiting on one's own forked children needs no privilege at all. No capabilities, user namespaces, or root are required.\nUI:N - The attacker's own process performs every step: submitting the waitid SQE, forking and signalling the children that generate wakeups, and issuing the concurrent cancel. No action by any other user is needed.\nS:U - The use-after-free corrupts kernel heap memory and control flow within the same kernel security authority, yielding standard local privilege escalation. No VM, IOMMU, or other security-boundary crossing is involved.\nC:H - This is a use-after-free on a `struct io_waitid_async` allocated from a general-purpose kmalloc slab, which the attacker can reclaim and shape via heap spraying. The stale wait-queue entry is then dereferenced by `__wake_up_common()` and `list_del_init()`, giving a read primitive over reclaimed kernel memory that can be leveraged for arbitrary kernel memory disclosure.\nI:H - `list_del_init()` on the freed entry performs `prev->next = next; next->prev = prev` using pointers read from attacker-reclaimed memory, yielding a controlled write of a controlled pointer to a controlled address. Additionally `__wake_up_common()` calls `curr->func(...)` on the freed entry, providing a direct indirect-call/control-flow hijack primitive leading to kernel code execution.\nA:H - Even without weaponization, the dangling wait-queue entry and the list-corrupting `list_del_init()` on freed memory produce KASAN splats, list debug BUGs, and kernel oopses/panics — this is exactly how syzbot detected it. The race can be re-triggered in a tight loop, so an unprivileged user can crash the machine at will."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:07:20.600Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.12.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.17.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.18"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}