{ "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" } } ] } }