GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

CVE-2025-39963 (GCVE-0-2025-39963)

Vulnerability from cvelistv5 – Published: 2025-10-09 12:13 – Updated: 2026-08-05 12:06
VLAI
Title
io_uring: fix incorrect io_kiocb reference in io_link_skb
Summary
In the Linux kernel, the following vulnerability has been resolved: io_uring: fix incorrect io_kiocb reference in io_link_skb In io_link_skb function, there is a bug where prev_notif is incorrectly assigned using 'nd' instead of 'prev_nd'. This causes the context validation check to compare the current notification with itself instead of comparing it with the previous notification. Fix by using the correct prev_nd parameter when obtaining prev_notif.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 6fe4220912d19152a26ce19713ab232f4263018d , < a89c34babc2e5834aa0905278f26f4dbe4b26b76 (git)
Affected: 6fe4220912d19152a26ce19713ab232f4263018d , < 50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a (git)
Affected: 6fe4220912d19152a26ce19713ab232f4263018d , < 2c139a47eff8de24e3350dadb4c9d5e3426db826 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.10
Unaffected: 0 , < 6.10 (semver)
Unaffected: 6.12.49 , ≤ 6.12.* (semver)
Unaffected: 6.16.9 , ≤ 6.16.* (semver)
Unaffected: 6.17 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "io_uring/notif.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "a89c34babc2e5834aa0905278f26f4dbe4b26b76",
              "status": "affected",
              "version": "6fe4220912d19152a26ce19713ab232f4263018d",
              "versionType": "git"
            },
            {
              "lessThan": "50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a",
              "status": "affected",
              "version": "6fe4220912d19152a26ce19713ab232f4263018d",
              "versionType": "git"
            },
            {
              "lessThan": "2c139a47eff8de24e3350dadb4c9d5e3426db826",
              "status": "affected",
              "version": "6fe4220912d19152a26ce19713ab232f4263018d",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "io_uring/notif.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.10"
            },
            {
              "lessThan": "6.10",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.49",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.16.*",
              "status": "unaffected",
              "version": "6.16.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.49",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.16.9",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17",
                  "versionStartIncluding": "6.10",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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 \u0027nd\u0027 instead of \u0027prev_nd\u0027. 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": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "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 \u2014 `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 \u2014 ring creation, socket setup, and both zerocopy sends \u2014 inside their own process with no victim action required.\nS:U - The corruption is confined to the kernel\u0027s own io_uring request cache and completion lists; no virtualization, IOMMU, or other security-authority boundary is crossed.\nC:H - Corrupting another ring\u0027s `compl_reqs` list makes the same `io_kiocb` reachable from two live operations and posts CQEs into a foreign ring\u0027s 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 \u2014 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": {
        "dateUpdated": "2026-08-05T12:06:32.066Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "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"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39963",
    "datePublished": "2025-10-09T12:13:23.345Z",
    "dateReserved": "2025-04-16T07:20:57.149Z",
    "dateUpdated": "2026-08-05T12:06:32.066Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2025-39963",
      "date": "2026-09-16",
      "epss": "0.00151",
      "percentile": "0.04637"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-39963\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-10-09T13:15:32.517\",\"lastModified\":\"2026-07-30T06:24:01.333\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"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 \u0027nd\u0027 instead of \u0027prev_nd\u0027. 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\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"io_uring/notif.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6fe4220912d19152a26ce19713ab232f4263018d\",\"lessThan\":\"a89c34babc2e5834aa0905278f26f4dbe4b26b76\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6fe4220912d19152a26ce19713ab232f4263018d\",\"lessThan\":\"50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6fe4220912d19152a26ce19713ab232f4263018d\",\"lessThan\":\"2c139a47eff8de24e3350dadb4c9d5e3426db826\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"io_uring/notif.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.10\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.10\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.49\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.16.9\",\"lessThanOrEqual\":\"6.16.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.17\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"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\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9},{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"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\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-401\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.10\",\"versionEndExcluding\":\"6.12.49\",\"matchCriteriaId\":\"B5A5D976-D1DD-49E0-8391-4B3365905BD2\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"6.13\",\"versionEndExcluding\":\"6.16.9\",\"matchCriteriaId\":\"638DD910-1189-4F5E-98BF-2D436B695112\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*\",\"matchCriteriaId\":\"327D22EF-390B-454C-BD31-2ED23C998A1C\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*\",\"matchCriteriaId\":\"C730CD9A-D969-4A8E-9522-162AAF7C0EE9\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.17:rc3:*:*:*:*:*:*\",\"matchCriteriaId\":\"39982C4B-716E-4B2F-8196-FA301F47807D\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.17:rc4:*:*:*:*:*:*\",\"matchCriteriaId\":\"340BEEA9-D70D-4290-B502-FBB1032353B1\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.17:rc5:*:*:*:*:*:*\",\"matchCriteriaId\":\"47E4C5C0-079F-4838-971B-8C503D48FCC2\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:6.17:rc6:*:*:*:*:*:*\",\"matchCriteriaId\":\"5A4516A6-C12E-42A4-8C0E-68AEF3264504\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/2c139a47eff8de24e3350dadb4c9d5e3426db826\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/a89c34babc2e5834aa0905278f26f4dbe4b26b76\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-07-30T10:08:27+00:00",
      "cve": "CVE-2025-39963",
      "id": "CVE-2025-39963",
      "initial_release_date": "2025-10-09T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: io_uring: fix incorrect io_kiocb reference in io_link_skb",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-39963.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-11T16:37:07Z",
      "cve": "CVE-2025-39963",
      "id": "CVE-2025-39963",
      "initial_release_date": "2025-10-09T23:23:01Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "399",
      "product_status:known_not_affected": "540",
      "product_status:recommended": "162",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-39963",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-39963.json",
      "version": "34"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.