NFSD: Prevent client use-after-free during blocked-lock reaping
CVE-2026-90036 · published 16 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-2026-90036?
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: 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b to < 0d53a47c913d0bce3b5ec35c28cbcca4d015f33d, 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b to < 7081224a59a0ca4edcd62c068588f4d900199a18, 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b to < cd489b03587378645fe0d20142a33f1ed60bac98, 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b to < 6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0
- Linux Linux: 4.9
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 blocked-lock reaping
A bare lock owner -- its only remaining reference a blocked lock on
nn->blocked_locks_lru -- holds a raw pointer to its nfs4_client but
no reference keeping the client alive. When the per-net laundromat
reaps such a lock, freeing the nbl drops the owner reference
held through flc_owner, and the final nfs4_put_stateowner()
takes the client's cl_lock. Because the laundromat detaches the
nbl first, __destroy_client() no longer finds it, so a concurrent
force_expire_client() can free the client before nfs4_put_stateowner()
runs, dereferencing cl_lock in freed memory.
Pin the client with cl_rpc_users before dropping
nn->blocked_locks_lock, and skip clients already expiring, whose
blocked locks __destroy_client() frees while holding an owner
reference. Take nn->client_lock outside nn->blocked_locks_lock.
Every other site holds nn->blocked_locks_lock as a leaf, acquiring
no further lock, so placing nn->client_lock outside it cannot form
a lock-order cycle.
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/0d53a47c913d0bce3b5ec35c28cbcca4d015f33d
- git.kernel.org/stable/c/7081224a59a0ca4edcd62c068588f4d900199a18
- git.kernel.org/stable/c/cd489b03587378645fe0d20142a33f1ed60bac98
- git.kernel.org/stable/c/6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0
- git.kernel.org/stable/c/9026932ac8be4d0ae01db47f23619a98cc57b671
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON