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CVE-2026-89662

CRITICALCVSS 9.8/10EPSS 0.61%

Last modified

CVE-2026-89662 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent lock owner use-after-free during client teardown __destroy_client() releases a client's open owners, but a lock owner whose only reference is a blocked lock (nbl) stays on cl_ownerstr_hashtbl. client_has_state() does not count a bare owner, so DESTROY_CLIENTID can reach __destroy_client() with such owners present. __destroy_client() then walks the table, calling remove_blocked_locks() on each owner without a reference. EPSS estimates a 0.61% chance of exploitation in the next 30 days.

Description

In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent lock owner use-after-free during client teardown __destroy_client() releases a client's open owners, but a lock owner whose only reference is a blocked lock (nbl) stays on cl_ownerstr_hashtbl. client_has_state() does not count a bare owner, so DESTROY_CLIENTID can reach __destroy_client() with such owners present. __destroy_client() then walks the table, calling remove_blocked_locks() on each owner without a reference. Freeing a blocked lock drops the owner reference held via flc_owner. The per-net laundromat reaps blocked locks from nn->blocked_locks_lru independently of client state. The two paths share blocked_locks_lock only for the list splice, not the owner's lifetime. The laundromat therefore frees the owner as __destroy_client() dereferences it, a NULL dereference in remove_blocked_locks(). nfsd4_release_lockowner() holds a reference across the same call; __destroy_client() does not. Hold cl_lock across the walk, taking a reference and unhashing each owner, then drop it before remove_blocked_locks() and nfs4_put_stateowner(), which take blocked_locks_lock and cl_lock.

Metrics

CVSS 3.1
9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability
0.61%

47.2th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 68ef3bc3166468678d5e1fdd216628c35bd1186f, < 42d7954b0a1907d4ef122aef94561952a033cdc3; >= 68ef3bc3166468678d5e1fdd216628c35bd1186f, < bb38ff8b4dafbbd1781ad37cd96722fdf2cd972a; >= 68ef3bc3166468678d5e1fdd216628c35bd1186f, < b8bad5a11416b26cc7fd4b18fba46d75ff636558; >= 68ef3bc3166468678d5e1fdd216628c35bd1186f, < 1ce74d1b7770e69735e8f8e509807af4ff9c8ee7; >= 68ef3bc3166468678d5e1fdd216628c35bd1186f, < a6ead6fff3a7d03e49845f048f7000a2e0d34431; >= 68ef3bc3166468678d5e1fdd216628c35bd1186f, < 4804c58f73a80d12df1de323bf97a164f6ee8743; >= 68ef3bc3166468678d5e1fdd216628c35bd1186f, < 8cf4ff0a7c083dd5e0067f517d63979b74b66649; >= 68ef3bc3166468678d5e1fdd216628c35bd1186f, < 5e2fa29d223a9a1e6a948e40b109d09081d1decd; e294c4c2d33b7307a89cdf31bec08a112d6a9297; 797bfd05d4040fbf766198b3cfcc1838002cc890; 0f44e9da465ea259b6c9f31a627f3c50a16e1679; >= 4.9.91, < 4.10; >= 4.14.31, < 4.15; >= 4.15.14, < 4.16
LinuxLinux4.16

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-89662?
In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent lock owner use-after-free during client teardown __destroy_client() releases a client's open owners, but a lock owner whose only reference is a blocked lock (nbl) stays on cl_ownerstr_hashtbl. client_has_state() does not count a bare owner, so DESTROY_CLIENTID can reach __destroy_client() with such owners present. __destroy_client() then walks the table, calling remove_blocked_locks() on each owner without a reference. Freeing a blocked lock drops the owner reference held via flc_owner. The per-net laundromat reaps blocked locks from nn->blocked_locks_lru independently of client state. The two paths share blocked_locks_lock only for the list splice, not the owner's lifetime. The laundromat therefore frees the owner as __destroy_client() dereferences it, a NULL dereference in remove_blocked_locks(). nfsd4_release_lockowner() holds a reference across the same call; __destroy_client() does not. Hold cl_lock across the walk, taking a reference and unhashing each owner, then drop it before remove_blocked_locks() and nfs4_put_stateowner(), which take blocked_locks_lock and cl_lock.
How severe is CVE-2026-89662?
CVE-2026-89662 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.61% probability of exploitation in the next 30 days.
How do I fix CVE-2026-89662?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST