{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-39698","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2025-04-16T07:20:57.115Z","datePublished":"2025-09-05T17:21:04.360Z","dateUpdated":"2026-08-05T12:04:39.909Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:04:39.909Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring/futex: ensure io_futex_wait() cleans up properly on failure\n\nThe io_futex_data is allocated upfront and assigned to the io_kiocb\nasync_data field, but the request isn't marked with REQ_F_ASYNC_DATA\nat that point. Those two should always go together, as the flag tells\nio_uring whether the field is valid or not.\n\nAdditionally, on failure cleanup, the futex handler frees the data but\ndoes not clear ->async_data. Clear the data and the flag in the error\npath as well.\n\nThanks to Trend Micro Zero Day Initiative and particularly ReDress for\nreporting this."}],"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 purely through the io_uring interface — `io_uring_setup(2)` plus an SQE with `IORING_OP_FUTEX_WAIT` — which requires local code execution on the system. There is no remote or adjacent-network path into `io_futex_wait()`.\nAC:L - The failure path is hit deterministically by submitting a FUTEX_WAIT SQE whose `futex_val` does not match `*uaddr` (returns -EWOULDBLOCK) or with an unmapped `uaddr` (-EFAULT); no race or timing window is involved. The attacker also fully controls request recycling and heap grooming, since the freed `io_futex_data` lands in a general-purpose kmalloc cache and the sequence can be repeated arbitrarily.\nPR:L - `sysctl_io_uring_disabled` defaults to 0, so any unprivileged user can create a ring, and `IORING_OP_FUTEX_WAIT` requires no file, no capability, and no privileged setup (`io_futex_prep` only validates futex2 flags). No root or namespace trickery is needed.\nUI:N - The attacker submits all SQEs from their own process and drives the entire sequence — failing futex wait, request recycling, then POLL_ADD — with no action by any other user. No victim process or administrator involvement is required.\nS:U - The use-after-free occurs in kernel heap memory managed by the same kernel security authority as the attacking process. Exploitation yields kernel privilege escalation rather than crossing a VM, IOMMU, or other separate security boundary.\nC:H - The stale `req->async_data` is dereferenced as a `struct io_poll *` in `__io_queue_proc()` (`(*poll_ptr)->head`), reading freed slab memory that the attacker can reclaim and shape, giving a controllable kernel-memory read/type-confusion primitive. Consistent with the guidance, a use-after-free of an attacker-reclaimable heap object is scored as High confidentiality impact.\nI:H - The dangling pointer is stored in a recycled `io_kiocb` and later treated as a live `struct io_poll`, so poll teardown (`io_poll_remove_entry()`'s `list_del_init(&poll->wait.entry)` / `poll->head = NULL`) and `__io_futex_cancel()`'s unguarded `futex_unqueue(&ifd->q)` operate on attacker-reclaimed memory. This is the classic io_uring UAF/type-confusion shape that is leveraged into arbitrary write and local privilege escalation, which is why ZDI reported it.\nA:H - Dereferencing the freed `io_futex_data` as an `io_poll` reliably produces slab corruption, KASAN splats, and kernel oopses/panics even without a successful exploit. Any unprivileged user can repeat the trigger at will to crash the machine."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/futex.c"],"versions":[{"version":"194bb58c6090e39bd7d9b9c888a079213628e1f6","lessThan":"d9f93172820a53ab42c4b0e5e65291f4f9d00ad2","status":"affected","versionType":"git"},{"version":"194bb58c6090e39bd7d9b9c888a079213628e1f6","lessThan":"d34c04152df517c59979b4bf2a47f491e06d3256","status":"affected","versionType":"git"},{"version":"194bb58c6090e39bd7d9b9c888a079213628e1f6","lessThan":"508c1314b342b78591f51c4b5dadee31a88335df","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/futex.c"],"versions":[{"version":"6.7","status":"affected"},{"version":"0","lessThan":"6.7","status":"unaffected","versionType":"semver"},{"version":"6.12.44","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.16.4","lessThanOrEqual":"6.16.*","status":"unaffected","versionType":"semver"},{"version":"6.17","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.12.44"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.16.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7","versionEndExcluding":"6.17"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/d9f93172820a53ab42c4b0e5e65291f4f9d00ad2"},{"url":"https://git.kernel.org/stable/c/d34c04152df517c59979b4bf2a47f491e06d3256"},{"url":"https://git.kernel.org/stable/c/508c1314b342b78591f51c4b5dadee31a88335df"},{"url":"https://www.zerodayinitiative.com/advisories/ZDI-25-915/"}],"title":"io_uring/futex: ensure io_futex_wait() cleans up properly on failure","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"metrics":[{"cvssV3_1":{"scope":"CHANGED","version":"3.1","baseScore":8.8,"attackVector":"LOCAL","baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","integrityImpact":"HIGH","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"HIGH"}},{"other":{"type":"ssvc","content":{"id":"CVE-2025-39698","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2025-09-26T03:55:13.138774Z"}}}],"problemTypes":[{"descriptions":[{"lang":"en","type":"CWE","cweId":"CWE-672","description":"CWE-672 Operation on a Resource after Expiration or Release"}]}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-02-26T17:49:11.880Z"}}]}}