Bug 2516364 (CVE-2026-72389)

Summary: CVE-2026-72389 kernel: bridge: stp: Fix a potential use-after-free when deleting a bridge
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's bridge Spanning Tree Protocol (STP) module. A missing check in the br_topology_change_detection() function allows a topology change timer to be armed while a bridge is administratively down. This can be exploited by an attacker to trigger a use-after-free vulnerability when the bridge is deleted, potentially leading to a denial of service or arbitrary code execution.
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Description OSIDB Bzimport 2026-08-15 06:08:38 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bridge: stp: Fix a potential use-after-free when deleting a bridge

The three STP timers are not supposed to be armed while the bridge is
administratively down. They are synchronously deactivated when the
bridge is put administratively down and the various call sites check for
'IFF_UP' before arming them.

This check is missing from br_topology_change_detection() and it is
possible to engineer a situation in which the topology change timer is
armed while the bridge is administratively down, resulting in a
use-after-free [1] when the bridge is deleted.

Fix by adding the missing check and for good measures synchronously
shutdown the three timers when the bridge is deleted.

[1]
ODEBUG: free active (active state 0) object: ffff88811662b9b0 object type: timer_list hint: br_topology_change_timer_expired (net/bridge/br_stp_timer.c:120)
WARNING: lib/debugobjects.c:629 at debug_print_object+0x1bc/0x450, CPU#9: ip/359