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TI-2026-81838 Aliases CVE-2026-99131GHSA-5g3h-v4h7-rrh3

Capability check flaw in Linux kernel XFS lets users evade quotas

Priority LOW 36Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · Low · High
Fix status
Partial Red Hat: 4 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.

Summary

The Linux kernel XFS filesystem from 5.18 is affected, with fixes in the stable branches listed in the solution. A capability check in XFS uses the task's real credentials instead of its effective credentials, which lets quota enforcement be skipped. An unauthenticated remote attacker can change a file's group ID through an NFS client and exceed the group's quota.

Written with Claude Haiku 5.5 from the sources below · 2026-10-31

Description from the CNA

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()

Why it matters now

EPSS 0.0045 39th percentileScored 2026-11-07
Fix Partial Linux (Linux): 6.1.191, 6.6.161, 6.12.115 +3Red Hat: 4 without a fix

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux5.18 and later6.1.191, 6.6.161, 6.12.115, 6.18.59, 7.2.13, 7.3Patch availableCNA
  • Linux VendorLinux Affected 5.18 and later Fixed in 6.1.191, 6.6.161, 6.12.115, 6.18.59, 7.2.13, 7.3 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*——Linux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions — — ·Linux

Remediation

Upgrade to Linux kernel 6.1.191, 6.6.161, 6.12.115, 6.18.59, 7.2.13 or 7.3. Red Hat lists Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 and Red Hat OpenShift Container Platform 5 as affected with no fix plan available.

Written with Claude Haiku 5.5 from the sources below · 2026-10-31

  • Fix · CNA Linux (Linux) Fixed in 6.1.191, 6.6.161, 6.12.115, 6.18.59, 7.2.13, 7.3

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 10AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 9AffectedNo fix yet: Fix deferred
Red Hat OpenShift Container Platform 4AffectedNo fix yet: Fix deferred
Red Hat OpenShift Container Platform 5AffectedNo fix yet: Fix deferred
Not affected: 4 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat OpenShift Container Platform 4

Timeline

  1. 2026-10-28 Threatist record created from CVE-2026-99131
  2. 2026-10-28 Alias added: GHSA-5g3h-v4h7-rrh3
  3. 2026-10-29 Affected versions changed · Red Hat
  4. 2026-10-29 CVSS score added · Red Hat
  5. 2026-10-30 Affected versions changed · Red Hat
  6. 2026-10-30 Fix available: Linux/Linux@29f994db0447104a7a52fb6495193c80007cb66a, Linux/[email protected], Linux/[email protected] +3 · CNA
  7. 2026-10-30 3 new references · CNA
  8. 2026-10-31 CVSS score added · CNA

References

Other 6

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2021-02452 Incorrect authorization in Ubuntu linux kernel KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
See all 21741 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences