CVE intelligence

CVE-2026-31504

Vulnerability intelligence

Published Apr 22, 2026Sources checked Nov 12, 2026

7.8HIGHCVSS out of 10

What this means

Review the available evidence

CVE-2026-31504 and is rated High severity with a CVSS score of 7.8. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Sep 25, 2026

CBL-Mariner Releases Release Notes

Vendor-listed releases

6.6.134.1-2

CISA KEVNot listedBased on the latest collected catalog

EPSS0.1%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-31504?

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.

Source: NVD