CVE-2026-31504

CVE Details

Release Date:	2026-04-22
Impact:	Important	What is this?

Description

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.

See more information about CVE-2026-31504 from MITRE CVE dictionary and NIST NVD

NOTE: The following CVSS metrics and score provided are preliminary and subject to review.

CVSS v3 metrics

Base Score:	7.0
Vector String:	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Version:	3.1
Attack Vector:	Local
Attack Complexity:	High
Privileges Required:	Low
User Interaction:	None
Scope:	Unchanged
Confidentiality Impact:	High
Integrity Impact:	High
Availability Impact:	High

Errata information

Platform	Errata	Release Date
Oracle Linux version 8 (kernel-uek)	ELSA-2026-50318	2026-06-15
Oracle Linux version 9 (kernel-uek)	ELSA-2026-50318	2026-06-15