{"id":"CVE-2025-39963","state":"PUBLISHED","title":"io_uring: fix incorrect io_kiocb reference in io_link_skb","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring: fix incorrect io_kiocb reference in io_link_skb\n\nIn io_link_skb function, there is a bug where prev_notif is incorrectly\nassigned using 'nd' instead of 'prev_nd'. This causes the context\nvalidation check to compare the current notification with itself instead\nof comparing it with the previous notification.\n\nFix by using the correct prev_nd parameter when obtaining prev_notif.","publishedAt":"2025-10-09T12:13:23.345Z","updatedAt":"2026-10-15T22:02:34.193Z","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":"6fe4220912d19152a26ce19713ab232f4263018d","status":"affected","lessThan":"a89c34babc2e5834aa0905278f26f4dbe4b26b76","versionType":"git"},{"version":"6fe4220912d19152a26ce19713ab232f4263018d","status":"affected","lessThan":"50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a","versionType":"git"},{"version":"6fe4220912d19152a26ce19713ab232f4263018d","status":"affected","lessThan":"2c139a47eff8de24e3350dadb4c9d5e3426db826","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/notif.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.12.49","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.16.9","status":"unaffected","lessThanOrEqual":"6.16.*","versionType":"semver"},{"version":"6.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/notif.c"]}],"references":["https://git.kernel.org/stable/c/a89c34babc2e5834aa0905278f26f4dbe4b26b76","https://git.kernel.org/stable/c/50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a","https://git.kernel.org/stable/c/2c139a47eff8de24e3350dadb4c9d5e3426db826"],"weaknesses":[],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/39xxx/CVE-2025-39963.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-39963","state":"PUBLISHED","datePublished":"2025-10-09T12:13:23.345Z","dateUpdated":"2026-10-15T22:02:34.193Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T07:20:57.149Z"},"containers":{"cna":{"title":"io_uring: fix incorrect io_kiocb reference in io_link_skb","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nio_uring: fix incorrect io_kiocb reference in io_link_skb\n\nIn io_link_skb function, there is a bug where prev_notif is incorrectly\nassigned using 'nd' instead of 'prev_nd'. This causes the context\nvalidation check to compare the current notification with itself instead\nof comparing it with the previous notification.\n\nFix by using the correct prev_nd parameter when obtaining prev_notif."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6fe4220912d19152a26ce19713ab232f4263018d","status":"affected","lessThan":"a89c34babc2e5834aa0905278f26f4dbe4b26b76","versionType":"git"},{"version":"6fe4220912d19152a26ce19713ab232f4263018d","status":"affected","lessThan":"50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a","versionType":"git"},{"version":"6fe4220912d19152a26ce19713ab232f4263018d","status":"affected","lessThan":"2c139a47eff8de24e3350dadb4c9d5e3426db826","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/notif.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.12.49","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.16.9","status":"unaffected","lessThanOrEqual":"6.16.*","versionType":"semver"},{"version":"6.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["io_uring/notif.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/a89c34babc2e5834aa0905278f26f4dbe4b26b76"},{"url":"https://git.kernel.org/stable/c/50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a"},{"url":"https://git.kernel.org/stable/c/2c139a47eff8de24e3350dadb4c9d5e3426db826"}],"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 by submitting `IORING_OP_SEND_ZC` SQEs on a local io_uring instance, requiring local process execution; the attacker is the sender, so no remote peer can drive the path.\nAC:L - A single unprivileged process deterministically sets up the condition by creating two rings/threads and issuing consecutive SEND_ZC requests on one shared TCP socket whose peer is not draining, and it controls both sides of the subsequent cross-ring `compl_reqs` race.\nPR:L - No capability check exists anywhere on the path — `io_uring_setup()`, `io_send_zc_prep()`, and `tcp_sendmsg_locked()` are all available to any unprivileged user with default `kernel.io_uring_disabled=0`.\nUI:N - The attacker performs the entire sequence — ring creation, socket setup, and both zerocopy sends — inside their own process with no victim action required.\nS:U - The corruption is confined to the kernel's own io_uring request cache and completion lists; no virtualization, IOMMU, or other security-authority boundary is crossed.\nC:H - Corrupting another ring's `compl_reqs` list makes the same `io_kiocb` reachable from two live operations and posts CQEs into a foreign ring's completion queue, yielding a use-after-free that can be groomed into an arbitrary kernel-memory read.\nI:H - `io_free_batch_list()` runs `io_put_file()`, `io_put_task()`, and `io_req_add_to_cache()` on the corrupted list, giving double-free of `req_cachep` objects and `struct file` refcount underflow — classic stepping stones to arbitrary write and local privilege escalation.\nA:H - Even without successful grooming, cross-context chaining reliably produces list corruption, leaked never-completed requests that hang task/ring teardown, and on 6.18-era kernels a `WARN_ON_ONCE` that panics under `panic_on_warn`."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:06:32.066Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.12.49"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.16.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.17"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2025-39963","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-15T21:55:14.622512Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-15T22:02:34.193Z"}}]}}}