CVE-2025-37921

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

vxlan: vnifilter: Fix unlocked deletion of default FDB entry

When a VNI is deleted from a VXLAN device in 'vnifilter' mode, the FDB

entry associated with the default remote (assuming one was configured)

is deleted without holding the hash lock. This is wrong and will result

in a warning [1] being generated by the lockdep annotation that was

added by commit ebe642067455 ("vxlan: Create wrappers for FDB lookup").

Reproducer:

# ip link add vx0 up type vxlan dstport 4789 external vnifilter local 192.0.2.1

# bridge vni add vni 10010 remote 198.51.100.1 dev vx0

# bridge vni del vni 10010 dev vx0

Fix by acquiring the hash lock before the deletion and releasing it

afterwards. Blame the original commit that introduced the issue rather

than the one that exposed it.

[1]

WARNING: CPU: 3 PID: 392 at drivers/net/vxlan/vxlan_core.c:417 vxlan_find_mac+0x17f/0x1a0

[...]

RIP: 0010:vxlan_find_mac+0x17f/0x1a0

[...]

Call Trace:

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/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References