Vulnerability-Lookup

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

Vulnerability from cvelistv5 – Published: 2025-10-09 12:13 – Updated: 2026-08-05 12:06

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

Linux mitre root

References

3 references

URL	Tags
https://git.kernel.org/stable/c/a89c34babc2e5834a…
https://git.kernel.org/stable/c/50a98ce1ea694f1ff…
https://git.kernel.org/stable/c/2c139a47eff8de24e…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: 6fe4220912d19152a26ce19713ab232f4263018d , < a89c34babc2e5834aa0905278f26f4dbe4b26b76 (git) Affected: 6fe4220912d19152a26ce19713ab232f4263018d , < 50a98ce1ea694f1ff8e87bc2f8f84096d1736f6a (git) Affected: 6fe4220912d19152a26ce19713ab232f4263018d , < 2c139a47eff8de24e3350dadb4c9d5e3426db826 (git)	guessed
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

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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
            "io_uring/notif.c"
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              "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`."
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    "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"
  },
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      "cve": "CVE-2025-39963",
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      "product_status:known_affected": "184",
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      "title": "kernel: io_uring: fix incorrect io_kiocb reference in io_link_skb",
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    "suse_vex": {
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      "cve": "CVE-2025-39963",
      "id": "CVE-2025-39963",
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      "title": "SUSE CVE CVE-2025-39963",
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}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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CVE-2025-39963 (GCVE-0-2025-39963)

Tags

Sightings

Nomenclature

Related by attack behaviour