{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2025-39963",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2025-04-16T07:20:57.149Z",
        "datePublished": "2025-10-09T12:13:23.345Z",
        "dateUpdated": "2026-08-05T12:06:32.066Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-08-05T12:06:32.066Z"
            },
            "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."
                }
            ],
            "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`."
                        }
                    ]
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "io_uring/notif.c"
                    ],
                    "versions": [
                        {
                            "version": "6fe4220912d19152a26ce19713ab232f4263018d",
                            "lessThan": "a89c34babc2e5834aa0905278f26f4dbe4b26b76",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "6fe4220912d19152a26ce19713ab232f4263018d",
                            "lessThan": "50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "6fe4220912d19152a26ce19713ab232f4263018d",
                            "lessThan": "2c139a47eff8de24e3350dadb4c9d5e3426db826",
                            "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/notif.c"
                    ],
                    "versions": [
                        {
                            "version": "6.10",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "6.10",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.49",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.16.9",
                            "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": "6.10",
                                    "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"
                                }
                            ]
                        }
                    ]
                }
            ],
            "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"
                }
            ],
            "title": "io_uring: fix incorrect io_kiocb reference in io_link_skb",
            "x_generator": {
                "engine": "bippy-1.2.0"
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    }
}