CVE-2023-54121

Cross-file reads and writes via extent-map underflow

Published Dec 24, 2025 · Updated Dec 24, 2025

Memory corruption in the Linux btrfs filesystem allows local users to read or overwrite filesystem data during relocation. btrfs_drop_extent_map_range retains the original length after skipping a pinned extent, so split arithmetic underflows and inserts an overlapping extent map. An unprivileged account with write access to a mounted btrfs filesystem can shape extents while automatic or scheduled relocation triggers cross-file disclosure, corruption, a forced read-only remount, or a kernel panic.

CVSS severity7.8
High
EPSS probability0.16%
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

Memory corruption in the Linux btrfs filesystem allows local users to read or overwrite filesystem data during relocation. btrfs_drop_extent_map_range retains the original length after skipping a pinned extent, so split arithmetic underflows and inserts an overlapping extent map. An unprivileged account with write access to a mounted btrfs filesystem can shape extents while automatic or scheduled relocation triggers cross-file disclosure, corruption, a forced read-only remount, or a kernel panic.

The record

CVE
CVE-2023-54121
Published
Dec 24, 2025
Updated
Dec 24, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1005, T1499, T1565.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 24, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 24, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.33
  2. Affected versionversion=55ef68990029fcd8d04d42fc184aa7fb18cf309e <9f68e2105dd96cf0fafffffafb2337fbd0fbae1f
  3. Affected versionversion=55ef68990029fcd8d04d42fc184aa7fb18cf309e <b43a4c99d878cf5e59040e45c96bb0a8358bfb3b
  4. Affected versionversion=55ef68990029fcd8d04d42fc184aa7fb18cf309e <c962098ca4af146f2625ed64399926a098752c9c
  5. Affected versionversion=c87afd35a28b2661a2626a1b28e9fd69adcad9f9

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.33; version=55ef68990029fcd8d04d42fc184aa7fb18cf309e <9f68e2105dd96cf0fafffffafb2337fbd0fbae1f; version=55ef68990029fcd8d04d42fc184aa7fb18cf309e <b43a4c99d878cf5e59040e45c96bb0a8358bfb3b; version=55ef68990029fcd8d04d42fc184aa7fb18cf309e <c962098ca4af146f2625ed64399926a098752c9c; version=c87afd35a28b2661a2626a1b28e9fd69adcad9f9

Published CVSS scores

7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1005Data from Local System
T1499Endpoint Denial of Service
T1565.001Stored Data Manipulation

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