CVE-2025-21872

Boot interruption via repeated MOK table remapping

Published Mar 27, 2025 · Updated May 11, 2026

Improper resource allocation in Linux kernel EFI MOK handling allows local users to interrupt startup via an oversized MOK variable table. During efi_mokvar_table_init(), each loop iteration remaps the entire growing table through early_memmap() instead of mapping only the current entry header. Local low-privileged access is required; exceeding early mapping limits produces a traceback and prevents the table from being mapped during boot.

CVSS severity5.5
Medium
EPSS probability0.20%
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

Improper resource allocation in Linux kernel EFI MOK handling allows local users to interrupt startup via an oversized MOK variable table. During efi_mokvar_table_init(), each loop iteration remaps the entire growing table through early_memmap() instead of mapping only the current entry header. Local low-privileged access is required; exceeding early mapping limits produces a traceback and prevents the table from being mapped during boot.

The record

CVE
CVE-2025-21872
Published
Mar 27, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 27, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record 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=5.10
  2. Affected versionversion=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <2b90e7ace79774a3540ce569e000388f8d22c9e0
  3. Affected versionversion=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <46c0454ffb78ce9d3355a3cccac86383ea8ddd55
  4. Affected versionversion=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <65f4aebb8127708ba668dd938e83b8558abfc5cd
  5. Affected versionversion=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <97bd560b6cc4c26386a53b4881bf03e96f9ba03a
  6. Affected versionversion=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <ea3f0b362dfe4ef885ef812bfaf4088176422c91

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.10; version=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <2b90e7ace79774a3540ce569e000388f8d22c9e0; version=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <46c0454ffb78ce9d3355a3cccac86383ea8ddd55; version=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <65f4aebb8127708ba668dd938e83b8558abfc5cd; version=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <97bd560b6cc4c26386a53b4881bf03e96f9ba03a; version=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <ea3f0b362dfe4ef885ef812bfaf4088176422c91

Published CVSS scores

5.5CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5Amazon LinuxCVSS: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 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

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