CVE-2021-46951

Kernel crash via cumulative TPM log-size subtraction

Published Feb 27, 2024 · Updated May 11, 2026

Integer underflow in Linux 5.3 and affected later branches allows local users to crash the kernel through repeated TPM driver reloads. Each tpm_read_log_efi call subtracts final_events_preboot_size from the global efi_tpm_final_log_size, eventually passing an underflowed length to memcpy. Reaching the fault requires local privileges sufficient to load and unload a TPM2 driver repeatedly, and the demonstrated consequence is a kernel service interrupt.

CVSS severity5.5
Medium
EPSS probability0.24%
Next 30 days · Sep 17, 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

Integer underflow in Linux 5.3 and affected later branches allows local users to crash the kernel through repeated TPM driver reloads. Each tpm_read_log_efi call subtracts final_events_preboot_size from the global efi_tpm_final_log_size, eventually passing an underflowed length to memcpy. Reaching the fault requires local privileges sufficient to load and unload a TPM2 driver repeatedly, and the demonstrated consequence is a kernel service interrupt.

The record

CVE
CVE-2021-46951
Published
Feb 27, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-191
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 27, 2024CVE 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=166a2809d65b282272c474835ec22c882a39ca1b <2f12258b5224cfaa808c54fd29345f3c1cbfca76
  2. Affected versionversion=166a2809d65b282272c474835ec22c882a39ca1b <3818b753277f5ca0c170bf5b98e0a5a225542fcb
  3. Affected versionversion=166a2809d65b282272c474835ec22c882a39ca1b <48cff270b037022e37835d93361646205ca25101
  4. Affected versionversion=166a2809d65b282272c474835ec22c882a39ca1b <60a01ecc9f68067e4314a0b55148e39e5d58a51b
  5. Affected versionversion=166a2809d65b282272c474835ec22c882a39ca1b <ac07c557ca12ec9276c0375517bac7ae5be4e50c
  6. Affected versionversion=5.3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=166a2809d65b282272c474835ec22c882a39ca1b <2f12258b5224cfaa808c54fd29345f3c1cbfca76; version=166a2809d65b282272c474835ec22c882a39ca1b <3818b753277f5ca0c170bf5b98e0a5a225542fcb; version=166a2809d65b282272c474835ec22c882a39ca1b <48cff270b037022e37835d93361646205ca25101; version=166a2809d65b282272c474835ec22c882a39ca1b <60a01ecc9f68067e4314a0b55148e39e5d58a51b; version=166a2809d65b282272c474835ec22c882a39ca1b <ac07c557ca12ec9276c0375517bac7ae5be4e50c; version=5.3

Published CVSS scores

5.5Canonical UbuntuCVSS: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 11, 2026Sep 17, 2026
Latest reporting daySep 17, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-191Integer Underflow (Wrap or Wraparound)

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