---
id: "CVE-2026-99031"
kind: "vulnerability"
aliases: ["CVE-2026-99031"]
title: "Linux kernel bridge: multicast cleanup recursion can exhaust kernel stack"
severity: "unknown"
cvss: null
epss: 0.00209
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["bridge", "infrastructure", "kernel", "linux", "multicast"]
not_affected_if: []
published_at: "2026-10-23T13:17:26+00:00"
first_seen_at: "2026-10-23T21:57:33+00:00"
updated_at: "2026-10-25T12:38:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99031", "first_seen_at": "2026-10-23T21:57:33+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-99031", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# Linux kernel bridge: multicast cleanup recursion can exhaust kernel stack

Removing many automatically added multicast exclude-port groups on a Linux bridge recurses once per port, consuming one kernel stack frame each. With enough ports this hits the stack guard page and can crash the kernel.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-23T21:57:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99031
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-99031

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

net: bridge: avoid recursive multicast port cleanup

br_multicast_sg_del_exclude_ports() removes automatically added STAR_EXCL
port groups by calling br_multicast_del_pg(). For S,G entries, that
deletion calls back into br_multicast_sg_del_exclude_ports(), so a large
number of STAR_EXCL ports consumes one kernel stack frame per port and can
hit the stack guard page.

Keep the complete port-group deletion path for cleanup, but suppress the
S,G exclude-port cleanup while that helper is already walking the same
entry. Normal deletion callers retain the existing behavior.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_