Bug 2536313 (CVE-2026-90151)

Summary: CVE-2026-90151 kernel: NFSv4: remove callback IDR entry on client allocation failure
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 Linux kernel's Network File System version 4 (NFSv4) component. This vulnerability occurs when an NFSv4 client allocation fails, leaving a stale pointer to a freed client. A local attacker could potentially exploit this use-after-free condition by triggering a callback lookup, which may lead to memory corruption, causing system instability or a denial of service.
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Description OSIDB Bzimport 2026-09-17 17:19:21 UTC 
In the Linux kernel, the following vulnerability has been resolved:

NFSv4: remove callback IDR entry on client allocation failure

nfs4_alloc_client() allocates an NFSv4.0 callback identifier before it
finishes setting up the client. If any later initialization step fails,
the error path frees the nfs_client directly with nfs_free_client(). That
bypasses nfs_put_client(), which is where the callback IDR entry is
removed during normal teardown.

A failed allocation can therefore leave cb_ident_idr pointing at a freed
nfs_client. A later NFSv4.0 callback lookup by cb_ident would find the
stale pointer and take a reference to it.

Make the callback IDR removal helper callable by the allocation failure
path, and remove the callback identifier before freeing the client.

This was found by a local static-analysis checker for publish-before-free
lifetime bugs and confirmed by manual inspection.
Comment 1 Keith Grant 2026-09-23 17:33:10 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90151.mbox