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CVE-2026-99031: net: bridge: avoid recursive multicast port cleanup

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-23 · updated 2026-10-30

Description

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.

Affected products

• Linux: 5.10 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux 7.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/0ed8edcbcf2290dba13c1beeba27fc19ad38515b
• https://git.kernel.org/stable/c/26142868b0767e95e28b7a1237f58b292b54d1d9
• https://git.kernel.org/stable/c/2fb87c6025f90191516bee3ce14b42eb3e1cfed7
• https://git.kernel.org/stable/c/5158353121bae4f552cb677ce8c5c3ef52f93a0d
• https://git.kernel.org/stable/c/695a5a4c69c922d9296b2d7ad5f1ce8c6858fc64
• https://git.kernel.org/stable/c/6a7385f6605958aa69eeb185c91f45d77640d1e2
• https://git.kernel.org/stable/c/7931fb9181421953f3133b408b0f2e2b8dd68b61
• https://git.kernel.org/stable/c/d109141ba14652146089ef78b32d5e4d5285ebad

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