CVE-2021-47641

Kernel crash via zero framebuffer pixclock

Published Feb 26, 2025 · Updated May 11, 2026

Divide-by-zero in Linux cirrusfb before 5.18 allows local users to crash the kernel through a framebuffer ioctl with a zero pixclock. cirrusfb_check_pixclock passes the caller-controlled pixclock directly to PICOS2KHZ, whose conversion divides by that value without rejecting zero. A local user must be able to issue the mode-setting ioctl against an active cirrusfb device; successful exploitation raises a divide error and interrupts the host.

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

What happened

Divide-by-zero in Linux cirrusfb before 5.18 allows local users to crash the kernel through a framebuffer ioctl with a zero pixclock. cirrusfb_check_pixclock passes the caller-controlled pixclock directly to PICOS2KHZ, whose conversion divides by that value without rejecting zero. A local user must be able to issue the mode-setting ioctl against an active cirrusfb device; successful exploitation raises a divide error and interrupts the host.

The record

CVE
CVE-2021-47641
Published
Feb 26, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-369, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 26, 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

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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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1d3fb46439ad4e8f0c5739eb33d1875ac9e0f135
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <40b13e3d85744210db13457785646634e2d056bd
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <45800c42ef000f417270bcfc08630e42486fca99
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <53a2088a396cfa1da92690a1da289634cd73bf0d
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5c6f402bdcf9e7239c6bc7087eda71ac99b31379
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6fe23ff94e7840097202e85c148688940b37c9b1
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8c7e2141fb89c620ab4e41512e262fbf25b8260d
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c656d04247a2654ede5cead2ecbf83431dad5261
  9. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e498b504f8c81b07efab9febf8503448de4dc9cf
  10. Affected versionversion=2.6.12

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1d3fb46439ad4e8f0c5739eb33d1875ac9e0f135; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <40b13e3d85744210db13457785646634e2d056bd; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <45800c42ef000f417270bcfc08630e42486fca99; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <53a2088a396cfa1da92690a1da289634cd73bf0d; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5c6f402bdcf9e7239c6bc7087eda71ac99b31379; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6fe23ff94e7840097202e85c148688940b37c9b1; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8c7e2141fb89c620ab4e41512e262fbf25b8260d; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c656d04247a2654ede5cead2ecbf83431dad5261; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e498b504f8c81b07efab9febf8503448de4dc9cf; version=2.6.12

Published CVSS scores

5.5CISA-ADPCVSS: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.

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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

CWE-369Divide By Zero
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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