CVE-2026-80838
Received Received - Intake

VxLAN FDB Use-After-Free in Linux Kernel

Publication date: 2026-09-04

Last updated on: 2026-09-04

Assigner: kernel.org

Description
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.

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Meta Information

Published
2026-09-04
Last Modified
2026-09-04
Generated
2026-09-04
AI Q&A
2026-09-04
EPSS Evaluated
N/A
NVD
CVE-2026-80838
EUVD
EUVD-2026-71288

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

Helpful Resources

Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a flaw in the VXLAN (Virtual Extensible LAN) module during FDB (Forwarding Database) flush operations. When a bulk flush is performed, the system incorrectly unlinks the last remote entry before destroying the parent FDB entry, leaving an invalid pointer accessible to RCU readers. This can lead to memory corruption or crashes when the receive learning path attempts to read or write to the invalid pointer.

Detection Guidance

This vulnerability is specific to the Linux kernel's VXLAN implementation and requires kernel-level inspection. Detection involves checking kernel logs for related errors or monitoring network traffic patterns. Commands like dmesg, journalctl -k, or checking VXLAN device configurations may help identify unusual behavior. No direct detection commands are provided in the context.

Impact Analysis

This vulnerability could cause system instability, crashes, or potential privilege escalation if exploited. Systems using VXLAN for network virtualization may experience unexpected behavior, data corruption, or denial of service due to memory corruption or invalid memory access.

Mitigation Strategies

Apply the latest Linux kernel patches or updates that address this issue. Monitor vendor advisories for kernel updates. If immediate patching is not possible, consider disabling VXLAN interfaces temporarily or restricting network access to reduce exposure until the fix is applied.

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