Cloudanix VulnDB

CVE-2023-53450

None

CVSS

—

EPSS

0.2%

Published

Oct 1, 2025

CISA due date

—

Cloudanix analysis

Schedule a fix SSVC: Track

A flaw in handling certain damaged file system data can cause computers to crash unexpectedly until the software is updated.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Moderate
Impact
Denial Of Service
Component
OS kernel
Class
Denial of service
Remediation
Patch
Effort
Low
Patch risk
Low

What it actually does

Corrupted ext4 superblock with oversized s_first_data_block causes underflow in block group calculation inside ext4_mb_release_group_pa, hitting a BUG_ON that crashes the kernel.

Why it matters to the business

Systems using affected ext4 implementations can be forced into unexpected restarts or halts, interrupting services and requiring manual recovery; the low EPSS and lack of KEV listing indicate limited real-world exploitation urgency.

How an attack unfolds

An attacker with write access to the mounted ext4 superblock (via local privileges or another flaw) overwrites s_first_data_block to an extreme value; subsequent ext4 block allocation or release operations trigger the underflow and kernel panic.

How to fix it

Upgrade affected packages to the listed fixed versions: janus (Debian:12) and janus (Debian:14) to 0.10.1-1; apply kernel updates that replace the BUG_ON with an ext4_warning in ext4_mb_release_group_pa.

How to confirm the fix worked

Confirm the running kernel contains the patched ext4 code that logs a warning instead of crashing on superblock underflow; re-test with a fuzzer that sets s_first_data_block to extreme values and verify only a warning is emitted.

Typical attack path

  1. Obtain sufficient privileges to modify the mounted ext4 superblock
  2. Overwrite s_first_data_block field with an excessively large value
  3. Trigger ext4 metadata operations that invoke ext4_mb_release_group_pa
  4. Cause integer underflow and BUG_ON panic to crash the system

How to detect it

Review kernel logs for ext4 warnings mentioning superblock or block group underflow; correlate with mount events or processes that access ext4 metadata shortly before crashes.

What your security team should do

  • Prioritize patching systems with high ext4 usage within standard maintenance windows given the low EPSS and absence from KEV
  • Monitor for unexpected kernel oops or ext4 warnings in system logs as a sign of attempted or accidental trigger
  • Restrict untrusted local write access to block devices containing ext4 file systems

The record

In the Linux kernel, the following vulnerability has been resolved: ext4: remove a BUG_ON in ext4_mb_release_group_pa() If a malicious fuzzer overwrites the ext4 superblock while it is mounted such that the s_first_data_block is set to a very large number, the calculation of the block group can underflow, and trigger a BUG_ON check. Change this to be an ext4_warning so that we don't crash the kernel.

Affected packages

Ecosystem Package Introduced Fixed
Linux Kernel 0 4.14.315
Linux Kernel 2.6.25 4.14.315

Related vulnerabilities