NFSD: Prevent client use-after-free during delegation revoke
CVE-2026-89659 · published 11 Sept 2026
How serious is it
- Severity: critical, CVSS score 9.8 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-89659?
Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.
Who is affected
- Linux Linux: 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 to < 94f0c73797c30a35812ffb32d11b8737d245c405, 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 to < 0dd276b1324a5e08e83c6f675919946c9f0d61c9, 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 to < 3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3, 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 to < 2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56
- Linux Linux: 3.10
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
In the Linux kernel, the following vulnerability has been resolved:
NFSD: Prevent client use-after-free during delegation revoke
A delegation stateid holds only a bare pointer to its owning
nfs4_client and does not keep it alive. The client survives its
stateids only because __destroy_client() drains cl_delegations and
cl_revoked before free_client() runs.
nfs4_laundromat() breaks that invariant: it unhashes an
expired delegation from cl_delegations, drops deleg_lock, then
revoke_delegation() relinks it onto cl_revoked under cl_lock. In that
window the delegation is on neither list, so client_has_state() can
report no remaining state.
Every teardown path first requires cl_rpc_users to be zero, but
the laundromat holds no such reference. A client whose recalled
delegation has just timed out can therefore reach free_client()
while revoke_delegation() is still about to dereference cl_lock,
a use-after-free.
Pin the client with cl_rpc_users across the revoke so teardown blocks
until it completes, then reap the delegation from cl_revoked. A client
already expiring reaps its own, so skip it and leave the delegation on
del_recall_lru.
Check your whole app
Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.
References
- git.kernel.org/stable/c/94f0c73797c30a35812ffb32d11b8737d245c405
- git.kernel.org/stable/c/0dd276b1324a5e08e83c6f675919946c9f0d61c9
- git.kernel.org/stable/c/3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3
- git.kernel.org/stable/c/2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56
- git.kernel.org/stable/c/4683ca76b3b7e5808338491c6eb3c20e6b4894d5
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON