CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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8DescriptionNVD
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.
AnalysisAI
Use-after-free in Linux kernel packet socket handling allows local attackers with low privileges to achieve kernel memory corruption, potentially leading to privilege escalation, information disclosure, or denial of service. The vulnerability stems from a race condition in packet_release() where NETDEV_UP events can re-register a socket into a fanout group's array after cleanup begins but before the socket number is zeroed, leaving dangling pointers. …
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RemediationAI
Within 24 hours: Identify all systems running Linux kernel versions prior to 5.10.253, 5.15.203, 6.1.168, 6.6.131, 6.12.80, 6.18.21, 6.19.11, or 7.0 using kernel version audits and patch management tools. Within 7 days: Prioritize patching for production systems in multi-tenant or shared-access environments (highest risk); schedule kernel updates to affected versions listed above, with testing in non-production environments first. …
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-24881
GHSA-5v9p-3rfc-6rw2