Bug 2562644 (CVE-2026-99131) - CVE-2026-99131 kernel: kernel: xfs: Disk quota bypass via improper capability check
Summary: CVE-2026-99131 kernel: kernel: xfs: Disk quota bypass via improper capability...
Keywords:
Status: NEW
Alias: CVE-2026-99131
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-10-28 10:42 UTC by OSIDB Bzimport
Modified: 2026-10-29 13:12 UTC (History)
17 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-10-28 10:42:17 UTC
In the Linux kernel, the following vulnerability has been resolved:

xfs: fix capability check in xfs

An user reported a bug where he managed to evade group's quota
by changing a file's gid to a different group id the same user
belonged to, even though quotas were enforced on both gids and the
file's size was big enough to exceed the quota's hardlimit.

Commit eba0549bc7d1 replaced a capable() call by a
has_capability_noaudit() to prevent unnecessary selinux audit messages.
Turns out that both calls have slightly different semantics even though
their documentation seems similar. Where in a nutshell:

capable() - Tests the task's effective credentials
has_ns_capability_noaudit() - Tests the task's real credentials

This most of the time has no practical difference but in some cases like
changing attrs (specifically group id in this case) through a NFS client
this will allow the quota code to use XFS_QMOPT_FORCE_RES, effectively
bypassing quota accounting checks.

Using instead ns_capable_noaudit() should fix this issue and prevent
selinux audit messages.

This also fix the remaining calls to has_capability_noaudit()


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