Bug 2535223 (CVE-2026-90038)

Summary: CVE-2026-90038 kernel: NFSD: Prevent client use-after-free during export state revocation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Network File System Daemon (NFSD) component of the Linux kernel. This vulnerability, a use-after-free, occurs when the nfsd4_revoke_export_states() function improperly handles client state revocation. An administrator removing an export can trigger a race condition, potentially leading to system instability or a denial of service. This issue arises because a client lock is dropped while a state ID reference is still held, allowing the client to be freed prematurely.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-16 11:37:27 UTC 
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().
Comment 1 Keith Grant 2026-09-16 23:56:35 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90038.mbox