CVE-2026-80838
UnknownSummary
In the Linux kernel's vxlan module, there is a vulnerability involving an invalid pointer during FDB flush operations. When a filtered bulk flush removes all remotes from an FDB entry, the last remote is unlinked in vxlan_fdb_dst_destroy() and only afterwards the parent FDB entry is destroyed. During this interval, an RCU reader can find the parent entry, and first_remote_rcu() applies list_entry_rcu() to the empty list head, producing an invalid remote pointer that the receive learning path can read from and write to. The fix leaves the last remote linked and asks the caller to destroy the entire FDB entry.
Risk Assessment
The invalid pointer can lead to reads or writes to invalid memory, potentially causing system crashes or data integrity issues.
Recommendation
Apply the Linux kernel update containing the fix for vxlan. Monitor FDB flush operations in environments with many entries.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: vxlan: keep the last remote linked during FDB flush A non-nexthop FDB entry is expected to have at least one remote while it remains reachable through the FDB hash table. A filtered bulk flush violates this invariant when every remote matches: It unlinks the last remote in vxlan_fdb_dst_destroy() and only afterwards tells vxlan_flush() to destroy the parent FDB entry. An RCU reader can find the parent during this interval. first_remote_rcu() then applies list_entry_rcu() to the empty list head, producing an invalid remote pointer that the receive learning path can read from and write to. When a matching remote is the sole remaining remote, leave it linked and ask the caller to destroy the entire FDB entry. vxlan_fdb_destroy() keeps the remote attached while sending the deletion notification and removing the parent from the lookup structures.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS