Bug 2516694 (CVE-2026-72405)

Summary: CVE-2026-72405 kernel: net: udp_tunnel: prevent double queueing in udp_tunnel_nic_device_sync
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 UDP tunnel networking component. A race condition in the `udp_tunnel_nic_device_sync` function allows a work item to be double-queued. This can lead to a use-after-free vulnerability, where memory is prematurely freed while still active. A local attacker could potentially exploit this to cause a denial of service or other undefined system behavior.
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Description OSIDB Bzimport 2026-08-15 06:26:14 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net: udp_tunnel: prevent double queueing in udp_tunnel_nic_device_sync

Yue Sun reported a use-after-free and debugobjects warning in
udp_tunnel_nic_device_sync_work() during concurrent device operations.

The workqueue core clears the internal pending bit before invoking the
worker. At that point, a concurrent thread can queue the work again.
When the already running worker eventually clears the work_pending flag
to 0, it mistakenly clears the flag for the newly queued instance.
udp_tunnel_nic_unregister() then observes work_pending as 0 and frees
the structure while the second work item is still active in the queue,
leading to UAF.

Fix this by returning early in udp_tunnel_nic_device_sync() if
work_pending is already set, preventing redundant work queueing.
Comment 1 Keith Grant 2026-08-19 15:29:43 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081522-CVE-2026-72405-5a5c@gregkh/T