Bug 2532086 (CVE-2026-89687)

Summary:	CVE-2026-89687 kernel: nfsd: ensure nfsd_file_do_acquire() does not use a non-opened file
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	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
Whiteboard:
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Doc Text:	A flaw was found in the Linux kernel's Network File System Daemon (nfsd). The `nfsd_file_do_acquire()` function might attempt to use a file that has not been fully opened, as the `->atomic_open` operation could return success prematurely. While this scenario is considered highly improbable, it could lead to incorrect file operations and potential system instability or denial of service under specific, rare conditions.	Story Points:	---
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-11 20:27:27 UTC

In the Linux kernel, the following vulnerability has been resolved:

nfsd: ensure nfsd_file_do_acquire() does not use a non-opened file

->atomic_open is permitted to return success without actually opening
the file.  It indicates this by calling finish_no_open().
This means dentry_create() can return a file which hasn't been opened.
This is extremely unlikely as ->atomic_open handlers typically
use finish_no_open() only for already existing files, and dentry_create()
isn't called in that case, and the parent being locked should prevent
races.

However out of an abundance of caution it seems wise to teach nfsd to
only use the file returned by dentry_create() if FMODE_OPENED is set,
indicating that it has in fact been opened.

Comment 1 Mauro Matteo Cascella 2026-09-21 10:26:05 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89687.mbox