CVE-2023-34256

System crash via unchecked ext4 descriptor size

Published May 31, 2023 · Updated Mar 11, 2025

Out-of-bounds read in Linux kernel before 6.3.3 allows local users to crash the system by modifying a mounted ext4 block device. ext4_group_desc_csum uses the mutable on-disk s_desc_size field instead of the validated in-memory value when calculating the checksum length, so crc16 reads past the group descriptor buffer. Triggering the path requires privileged block-device access, and third parties dispute whether such access falls within the kernel threat model.

CVSS severity5.5
Medium
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds read in Linux kernel before 6.3.3 allows local users to crash the system by modifying a mounted ext4 block device. ext4_group_desc_csum uses the mutable on-disk s_desc_size field instead of the validated in-memory value when calculating the checksum length, so crc16 reads past the group descriptor buffer. Triggering the path requires privileged block-device access, and third parties dispute whether such access falls within the kernel threat model.

The record

CVE
CVE-2023-34256
Published
May 31, 2023
Updated
Mar 11, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-125, T1499
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. May 31, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 11, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo