CVE-2026-31504 (GCVE-0-2026-31504)

Vulnerability from cvelistv5 – Published: 2026-04-22 13:54 – Updated: 2026-05-11 22:10
VLAI
Title
net: fix fanout UAF in packet_release() via NETDEV_UP race
Summary
In the Linux kernel, the following vulnerability has been resolved: net: fix fanout UAF in packet_release() via NETDEV_UP race `packet_release()` has a race window where `NETDEV_UP` can re-register a socket into a fanout group's `arr[]` array. The re-registration is not cleaned up by `fanout_release()`, leaving a dangling pointer in the fanout array. `packet_release()` does NOT zero `po->num` in its `bind_lock` section. After releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex` still matches the bound device. A concurrent `packet_notifier(NETDEV_UP)` that already found the socket in `sklist` can re-register the hook. For fanout sockets, this re-registration calls `__fanout_link(sk, po)` which adds the socket back into `f->arr[]` and increments `f->num_members`, but does NOT increment `f->sk_ref`. The fix sets `po->num` to zero in `packet_release` while `bind_lock` is held to prevent NETDEV_UP from linking, preventing the race window. This bug was found following an additional audit with Claude Code based on CVE-2025-38617.
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
Linux Linux Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < ee642b1962caa9aa231c01abbd58bc453ae6b66e (git)
Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 42cfd7898eeed290c9fb73f732af1f7d6b0a703e (git)
Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 1b4c03f8892d955385c202009af7485364731bb9 (git)
Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 654386baef228c2992dbf604c819e4c7c35fc71b (git)
Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 75fe6db23705a1d55160081f7b37db9665b1880b (git)
Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6 (git)
Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < ceccbfc6de720ad633519a226715989cfb065af1 (git)
Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 42156f93d123436f2a27c468f18c966b7e5db796 (git)
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Linux Linux Affected: 3.1
Unaffected: 0 , < 3.1 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.168 , ≤ 6.1.* (semver)
Unaffected: 6.6.131 , ≤ 6.6.* (semver)
Unaffected: 6.12.80 , ≤ 6.12.* (semver)
Unaffected: 6.18.21 , ≤ 6.18.* (semver)
Unaffected: 6.19.11 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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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.

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  • 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.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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