Bug 2517086 (CVE-2026-74475)

Summary: CVE-2026-74475 kernel: vxlan: use neigh_ha_snapshot() in route_shortcircuit()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
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 VXLAN (Virtual Extensible LAN) implementation. An issue exists where the neighbor hardware address (MAC address) could be read incorrectly due to a lack of proper synchronization. This could lead to the system using a partially updated or corrupted MAC address, potentially causing network communication issues or unexpected behavior.
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Description OSIDB Bzimport 2026-08-15 12:49:31 UTC 
In the Linux kernel, the following vulnerability has been resolved:

vxlan: use neigh_ha_snapshot() in route_shortcircuit()

The neighbour hardware address n->ha can be updated asynchronously by the
neighbour subsystem, protected by n->ha_lock seqlock. Reading n->ha without
holding the seqlock loop can lead to torn reads or reading a partially updated
MAC address.

Use neigh_ha_snapshot() in route_shortcircuit() to safely copy n->ha under
read_seqbegin()/read_seqretry() lock protection before using it.

Note that arp_reduce() and neigh_reduce() seem to have the same issue
left for future patches.
Comment 1 TEJ RATHI 2026-08-17 13:15:06 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081535-CVE-2026-74475-a303@gregkh/T