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Fencer Vulns
medium 5.5

CVE-2023-53503 json

ext4: allow ext4_get_group_info() to fail

published 2025-10-01 13 mo ago modified 2026-11-05 3 d ago also EUVD-2025-32776

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 5%
public exploits
0
none known

Summary

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

ext4: allow ext4_get_group_info() to fail

Previously, ext4_get_group_info() would treat an invalid group number as BUG(), since in theory it should never happen. However, if a malicious attaker (or fuzzer) modifies the superblock via the block device while it is the file system is mounted, it is possible for s_first_data_block to get set to a very large number. In that case, when calculating the block group of some block number (such as the starting block of a preallocation region), could result in an underflow and very large block group number. Then the BUG_ON check in ext4_get_group_info() would fire, resutling in a denial of service attack that can be triggered by root or someone with write access to the block device.

For a quality of implementation perspective, it's best that even if the system administrator does something that they shouldn't, that it will not trigger a BUG. So instead of BUG'ing, ext4_get_group_info() will call ext4_error and return NULL. We also add fallback code in all of the callers of ext4_get_group_info() that it might NULL.

Also, since ext4_get_group_info() was already borderline to be an inline function, un-inline it. The results in a next reduction of the compiled text size of ext4 by roughly 2k.

Patch / fix

  • Linux Linux 5.10.181, 5.15.113, 6.1.30, 6.3.4, 6.4
  • linux Debian 12 6.1.37-1
  • linux Debian 14, Debian 13 6.3.7-1

debian advisories DEBIAN-CVE-2023-53503

  • linux Ubuntu 22.04 LTS 5.15.0-83.92
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1044.49
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1041.49
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1041.46
  • linux-ibm Ubuntu 22.04 LTS 5.15.0-1037.40
  • linux-kvm Ubuntu 22.04 LTS 5.15.0-1041.46
  • linux-azure Ubuntu 22.04 LTS 5.15.0-1046.53
  • linux-gkeop Ubuntu 22.04 LTS 5.15.0-1027.32

ubuntu advisories UBUNTU-CVE-2023-53503

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-503.11.1.el9_5
  • rv RHEL 9 5.14.0-503.11.1.el9_5
  • perf RHEL 9 5.14.0-503.11.1.el9_5
  • rtla RHEL 9 5.14.0-503.11.1.el9_5
  • bpftool RHEL 9 7.4.0-503.11.1.el9_5
  • libperf RHEL 9 5.14.0-503.11.1.el9_5
  • kernel-rt RHEL 9 5.14.0-503.11.1.el9_5
  • kernel-64k RHEL 9 5.14.0-503.11.1.el9_5

red hat advisories RHSA-2024:10771RHSA-2024:9315

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2023-53503 updated cvss 5.7

kernel: ext4: allow ext4_get_group_info() to fail

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available “Fix deferred”
  • Red Hat CodeReady Linux Builder (v. 9) libperf 5.14.0-503.11.1.el9_5, kernel-debuginfo-common-s390x 5.14.0-503.11.1.el9_5, kernel-debuginfo-common-x86_64 5.14.0-503.11.1.el9_5, kernel-debuginfo-common-aarch64 5.14.0-503.11.1.el9_5, kernel-debuginfo-common-ppc64le 5.14.0-503.11.1.el9_5
    fixed: vendor fix RHSA-2024:9315
  • Red Hat CodeReady Linux Builder EUS (v.9.4) libperf 5.14.0-427.47.1.el9_4, kernel-debuginfo-common-s390x 5.14.0-427.47.1.el9_4, kernel-debuginfo-common-x86_64 5.14.0-427.47.1.el9_4, kernel-debuginfo-common-aarch64 5.14.0-427.47.1.el9_4, kernel-debuginfo-common-ppc64le 5.14.0-427.47.1.el9_4
    fixed: vendor fix RHSA-2024:10771
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-503.11.1.el9_5, perf 5.14.0-503.11.1.el9_5, rtla 5.14.0-503.11.1.el9_5, kernel-devel-matched 5.14.0-503.11.1.el9_5, kernel-64k-devel-matched 5.14.0-503.11.1.el9_5, kernel-debug-devel-matched 5.14.0-503.11.1.el9_5, +6 more
    fixed: vendor fix RHSA-2024:9315
  • Red Hat Enterprise Linux AppStream EUS (v.9.4) rv 5.14.0-427.47.1.el9_4, perf 5.14.0-427.47.1.el9_4, rtla 5.14.0-427.47.1.el9_4, kernel-devel-matched 5.14.0-427.47.1.el9_4, kernel-64k-devel-matched 5.14.0-427.47.1.el9_4, kernel-debug-devel-matched 5.14.0-427.47.1.el9_4, +6 more
    fixed: vendor fix RHSA-2024:10771
  • Red Hat Enterprise Linux BaseOS (v. 9) bpftool 7.4.0-503.11.1.el9_5, kernel 5.14.0-503.11.1.el9_5, kernel-64k 5.14.0-503.11.1.el9_5, kernel-core 5.14.0-503.11.1.el9_5, kernel-tools 5.14.0-503.11.1.el9_5, python3-perf 5.14.0-503.11.1.el9_5, +29 more
    fixed: vendor fix RHSA-2024:9315
  • Red Hat Enterprise Linux BaseOS EUS (v.9.4) bpftool 7.3.0-427.47.1.el9_4, kernel 5.14.0-427.47.1.el9_4, kernel-64k 5.14.0-427.47.1.el9_4, kernel-core 5.14.0-427.47.1.el9_4, kernel-tools 5.14.0-427.47.1.el9_4, python3-perf 5.14.0-427.47.1.el9_4, +28 more
    fixed: vendor fix RHSA-2024:10771
show 5 more
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-503.11.1.el9_5, kernel-rt-core 5.14.0-503.11.1.el9_5, kernel-rt-modules 5.14.0-503.11.1.el9_5, kernel-rt-debug-core 5.14.0-503.11.1.el9_5, kernel-rt-modules-core 5.14.0-503.11.1.el9_5, kernel-rt-debug-modules 5.14.0-503.11.1.el9_5, +4 more
    fixed: vendor fix RHSA-2024:9315
  • Red Hat Enterprise Linux Real Time EUS (v.9.4) kernel-rt 5.14.0-427.47.1.el9_4, kernel-rt-core 5.14.0-427.47.1.el9_4, kernel-rt-modules 5.14.0-427.47.1.el9_4, kernel-rt-debug-core 5.14.0-427.47.1.el9_4, kernel-rt-modules-core 5.14.0-427.47.1.el9_4, kernel-rt-debug-modules 5.14.0-427.47.1.el9_4, +4 more
    fixed: vendor fix RHSA-2024:10771
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-503.11.1.el9_5, kernel-rt-kvm 5.14.0-503.11.1.el9_5, kernel-rt-core 5.14.0-503.11.1.el9_5, kernel-rt-modules 5.14.0-503.11.1.el9_5, kernel-rt-debug-kvm 5.14.0-503.11.1.el9_5, kernel-rt-debug-core 5.14.0-503.11.1.el9_5, +6 more
    fixed: vendor fix RHSA-2024:9315
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.4) kernel-rt 5.14.0-427.47.1.el9_4, kernel-rt-kvm 5.14.0-427.47.1.el9_4, kernel-rt-core 5.14.0-427.47.1.el9_4, kernel-rt-modules 5.14.0-427.47.1.el9_4, kernel-rt-debug-kvm 5.14.0-427.47.1.el9_4, kernel-rt-debug-core 5.14.0-427.47.1.el9_4, +6 more
    fixed: vendor fix RHSA-2024:10771
  • Red Hat CodeReady Linux Builder (v. 9) kernel-cross-headers 5.14.0-503.11.1.el9_5 Red Hat Enterprise Linux 10 kernel Red Hat Enterprise Linux AppStream (v. 9) kernel-headers 5.14.0-503.11.1.el9_5
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 d ago

Exploit prediction

0.16% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.