Bug 2482052 (CVE-2026-45915)

Summary:	CVE-2026-45915 kernel: fat: avoid parent link count underflow in rmdir
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's handling of FAT (File Allocation Table) filesystems. When processing corrupted FAT images, the `rmdir` function can incorrectly decrement the parent directory's link count. This underflow can lead to a system instability or a denial of service (DoS) by triggering a kernel warning (`WARN_ON`) in the `drop_nlink()` function.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-05-27 15:08:57 UTC

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

fat: avoid parent link count underflow in rmdir

Corrupted FAT images can leave a directory inode with an incorrect
i_nlink (e.g. 2 even though subdirectories exist). rmdir then
unconditionally calls drop_nlink(dir) and can drive i_nlink to 0,
triggering the WARN_ON in drop_nlink().

Add a sanity check in vfat_rmdir() and msdos_rmdir(): only drop the
parent link count when it is at least 3, otherwise report a filesystem
error.

Comment 1 Keith Grant 2026-05-28 01:35:16 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026052723-CVE-2026-45915-ddf9@gregkh/T