Use-after-free in Linux kernel - CVE-2026-74480

Vulnerability details

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to a use-after-free in br_multicast_leave_group() in the bridge multicast handling code when processing fast-leave operations on port groups. A local user can trigger deletion of a matching port group to cause a denial of service.

The issue can occur when multicast-to-unicast had been enabled, allowing multiple port groups for the same port and group with different source MAC addresses, and is later disabled so entries are matched by port only.

Affected software

How to mitigate CVE-2026-74480

External References

• https://git.kernel.org/stable/c/0309ebbc570000ea0df11c06b69798e5860c5f6f
• https://git.kernel.org/stable/c/159ad90cb929c033308bb39a2c5f8fbf393b77aa
• https://git.kernel.org/stable/c/4695430e8132420bf8de94da3eb36a6cf35fde6b
• https://git.kernel.org/stable/c/4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4
• https://git.kernel.org/stable/c/a39789f211b8a4125f0c70e05b30cf715f4f187d

Related Security Bulletins

• Use-after-free in Linux kernel bridge
• Debian update for linux