Read the docs
TI-2021-21999 Aliases CVE-2021-47342GHSA-c5qq-qcr6-82vp

ext4: fix possible UAF when remounting r/o a mmp-protected file system

Priority LOW 34CWE-416Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 3 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.

Summary

In the Linux kernel, the following vulnerability has been resolved: ext4: fix possible UAF when remounting r/o a mmp-protected file system After commit 618f003199c6 ("ext4: fix memory leak in ext4_fill_super"), after the file system is remounted read-only, there is a race where the kmmpd thread can exit, causing sbi->s_mmp_tsk to point at freed memory, which the call to ext4_stop_mmpd() can trip over. Fix this by only allowing kmmpd() to exit when it is stopped via ext4_stop_mmpd(). Bug-Report-Link: <[email protected]>

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00245 15th percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.13, 5.10.77Red Hat: 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux5.12.18 to before 5.135.13Patch availableCNA
LinuxLinux5.10.51 to before 5.10.775.10.77Patch availableCNA
  • Linux VendorLinux Affected 5.12.18 to before 5.13 Fixed in 5.13 Patch available CNA
  • Linux VendorLinux Affected 5.10.51 to before 5.10.77 Fixed in 5.10.77 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*before 5.10.77; 5.11 to before 5.13.3VulnerableLinux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions before 5.10.77; 5.11 to before 5.13.3 Vulnerable ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 5.13
  • Fix · CNA Linux (Linux) Fixed in 5.10.77

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 7AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 8AffectedNo fix yet
Not affected: 1 product
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-47342
  2. 2026-10-03 Alias added: GHSA-c5qq-qcr6-82vp

References

Patch 3

  • 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-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
  • TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
See all 15278 →

Sources

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