CVE-2026-98487
Received Received - Intake

Bridge MDB Use-After-Free in Linux Kernel

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: net: bridge: mdb: restart port group walk after deletion br_mdb_flush_pgs() keeps a pointer-to-pointer cursor while walking mp->ports. br_multicast_del_pg() can re-enter the same MDB entry through br_multicast_sg_del_exclude_ports() and unlink other port groups. If the cursor points into one of those groups, the next iteration dereferences a stale cursor and can leave mp->ports pointing at freed memory. A following RTM_GETMDB exposes the dangling pointer: BUG: KASAN: slab-use-after-free in br_mdb_dump Read of size 8 br_mdb_dump rtnl_mdb_dump rtnl_dumpit netlink_dump Reset the cursor to mp->ports after every deletion. The deletion removes at least the selected group, so the restarted walk always makes progress.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98487
EUVD
EUVD-2026-103727

Affected Vendors & Products

Showing 5 associated CPEs
Vendor Product Version / Range
Linux Linux a6acb535afb2a3b688a7858f05b61f0433e480d5
Linux Linux a6acb535afb2a3b688a7858f05b61f0433e480d5
Linux Linux a6acb535afb2a3b688a7858f05b61f0433e480d5
Linux Linux a6acb535afb2a3b688a7858f05b61f0433e480d5
Linux Linux 6.8

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a use-after-free vulnerability in the Linux kernel's bridge multicast database (MDB) handling. It occurs when br_mdb_flush_pgs() walks through port groups while br_multicast_del_pg() deletes entries, causing a cursor to point to freed memory. This leads to a slab-use-after-free error when accessing the dangling pointer via RTM_GETMDB operations.

Impact Analysis

An attacker could exploit this to cause a kernel crash or execute arbitrary code with kernel privileges. This may lead to denial-of-service conditions or potential privilege escalation on affected systems running vulnerable Linux kernel versions with bridge networking enabled.

Mitigation Strategies

Update your Linux kernel to the latest stable version that includes the fix for CVE-2026-98487. Monitor kernel logs for slab-use-after-free errors in br_mdb_dump or related functions.

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