CVE-2021-46938

Kernel crash via stale device-mapper queue pointer

Published Feb 27, 2024 · Updated May 11, 2026

A double free in Linux allows local users to crash the kernel after a request-based device-mapper queue initialization failure. When dm_mq_init_request_queue() frees an unsuccessfully initialized blk_mq_tag_set without clearing its pointer, dm_mq_cleanup_mapped_device() later frees the same object during device removal. Reaching this path requires local access and permission to manage device-mapper devices; systems configured to panic on an oops can halt.

CVSS severity7.8
High
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

A double free in Linux allows local users to crash the kernel after a request-based device-mapper queue initialization failure. When dm_mq_init_request_queue() frees an unsuccessfully initialized blk_mq_tag_set without clearing its pointer, dm_mq_cleanup_mapped_device() later frees the same object during device removal. Reaching this path requires local access and permission to manage device-mapper devices; systems configured to panic on an oops can halt.

The record

CVE
CVE-2021-46938
Published
Feb 27, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-415, T1499.004
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

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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=1c357a1e86a4227a6b6059f2de118ae47659cebc <1cb02dc76f4c0a2749a02b26469512d6984252e9
  2. Affected versionversion=1c357a1e86a4227a6b6059f2de118ae47659cebc <6086f957416a6e87236c06079fcaba7a3998aeca
  3. Affected versionversion=1c357a1e86a4227a6b6059f2de118ae47659cebc <772b9f59657665af3b68d24d12b9d172d31f0dfb
  4. Affected versionversion=1c357a1e86a4227a6b6059f2de118ae47659cebc <8ae0185255eaf05bd66f4215c81e99bf01140fd9
  5. Affected versionversion=1c357a1e86a4227a6b6059f2de118ae47659cebc <8e947c8f4a5620df77e43c9c75310dc510250166
  6. Affected versionversion=1c357a1e86a4227a6b6059f2de118ae47659cebc <a992a283c0b77d0a7c2c348add0e6a21fb1dab67
  7. Affected versionversion=1c357a1e86a4227a6b6059f2de118ae47659cebc <b42c0a33dfdd451d9be62dd5de58c39f2750b6e3
  8. Affected versionversion=1c357a1e86a4227a6b6059f2de118ae47659cebc <d757bf4c69cda3c3ab7f775dfabbf5a80e2f6f9d
  9. Affected versionversion=4.6

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1c357a1e86a4227a6b6059f2de118ae47659cebc <1cb02dc76f4c0a2749a02b26469512d6984252e9; version=1c357a1e86a4227a6b6059f2de118ae47659cebc <6086f957416a6e87236c06079fcaba7a3998aeca; version=1c357a1e86a4227a6b6059f2de118ae47659cebc <772b9f59657665af3b68d24d12b9d172d31f0dfb; version=1c357a1e86a4227a6b6059f2de118ae47659cebc <8ae0185255eaf05bd66f4215c81e99bf01140fd9; version=1c357a1e86a4227a6b6059f2de118ae47659cebc <8e947c8f4a5620df77e43c9c75310dc510250166; version=1c357a1e86a4227a6b6059f2de118ae47659cebc <a992a283c0b77d0a7c2c348add0e6a21fb1dab67; version=1c357a1e86a4227a6b6059f2de118ae47659cebc <b42c0a33dfdd451d9be62dd5de58c39f2750b6e3; version=1c357a1e86a4227a6b6059f2de118ae47659cebc <d757bf4c69cda3c3ab7f775dfabbf5a80e2f6f9d; version=4.6

Published CVSS scores

7.8NVDCVSS: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.

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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-415Double Free
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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