CVE-2021-46910

ARM system crash via overflowing fixmap reservation

Published Feb 27, 2024 · Updated Aug 5, 2026

Kernel memory corruption in Linux 5.11 through 5.11.15 allows local users to crash ARM systems through high-CPU fixmap activity. With DEBUG_KMAP_LOCAL, doubled per-CPU slots let the fixmap region grow below its reserved window and collide with the virtual device-tree mapping; fixmap code then treats block entries as page-table entries and dereferences them with a low-memory-only translation. Reachability requires a 32-bit ARM kernel built with CONFIG_DEBUG_KMAP_LOCAL=y and a large NR_CPUS value, such as 32; the documented consequence is a boot-time kernel oops.

CVSS severity7.0
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Kernel memory corruption in Linux 5.11 through 5.11.15 allows local users to crash ARM systems through high-CPU fixmap activity. With DEBUG_KMAP_LOCAL, doubled per-CPU slots let the fixmap region grow below its reserved window and collide with the virtual device-tree mapping; fixmap code then treats block entries as page-table entries and dereferences them with a low-memory-only translation. Reachability requires a 32-bit ARM kernel built with CONFIG_DEBUG_KMAP_LOCAL=y and a large NR_CPUS value, such as 32; the documented consequence is a boot-time kernel oops.

The record

CVE
CVE-2021-46910
Published
Feb 27, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 27, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=2a15ba82fa6ca3f35502b3060f22118a938d2889 <5965ac11b1d5fcb38464728931649cd9df79c7c9
  2. Affected versionversion=2a15ba82fa6ca3f35502b3060f22118a938d2889 <d624833f5984d484c5e3196f34b926f9e71dafee
  3. Affected versionversion=5.11

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2a15ba82fa6ca3f35502b3060f22118a938d2889 <5965ac11b1d5fcb38464728931649cd9df79c7c9; version=2a15ba82fa6ca3f35502b3060f22118a938d2889 <d624833f5984d484c5e3196f34b926f9e71dafee; version=5.11

Published CVSS scores

7.0LinuxCVSS:3.1/AV:L/AC:H/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

No sourced classifications are available.

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

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Your stack

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