CVE-2021-47435

Kernel crash via device-mapper mempool race

Published May 22, 2024 · Updated May 11, 2026

NULL pointer dereference in the Linux kernel allows attackers to crash the system via concurrent device-mapper table swaps. In dm_io_dec_pending(), end_io_acct() wakes a table-swapping task before free_io() releases the I/O object, allowing bioset teardown to clear mempool->elements before mempool_free() uses it. Reaching the race requires a device-mapper table swap to overlap I/O completion; the bounded result is a kernel crash.

CVSS severityUnavailable
Unscored
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in the Linux kernel allows attackers to crash the system via concurrent device-mapper table swaps. In dm_io_dec_pending(), end_io_acct() wakes a table-swapping task before free_io() releases the I/O object, allowing bioset teardown to clear mempool->elements before mempool_free() uses it. Reaching the race requires a device-mapper table swap to overlap I/O completion; the bounded result is a kernel crash.

The record

CVE
CVE-2021-47435
Published
May 22, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. May 22, 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=2.6.37
  2. Affected versionversion=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <6e506f07c5b561d673dd0b0d8f7f420cc48024fb
  3. Affected versionversion=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <9e07272cca2ed76f7f6073f4444b1143828c8d87
  4. Affected versionversion=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <9fb7cd5c7fef0f1c982e3cd27745a0dec260eaed
  5. Affected versionversion=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <ad1393b92e5059218d055bfec8f4946d85ad04c4
  6. Affected versionversion=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <d208b89401e073de986dc891037c5a668f5d5d95
  7. Affected versionversion=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <d29c78d3f9c5d2604548c1065bf1ec212728ea61
  8. Affected versionversion=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <d35aef9c60d310eff3eaddacce301efe877e2b7c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.37; version=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <6e506f07c5b561d673dd0b0d8f7f420cc48024fb; version=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <9e07272cca2ed76f7f6073f4444b1143828c8d87; version=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <9fb7cd5c7fef0f1c982e3cd27745a0dec260eaed; version=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <ad1393b92e5059218d055bfec8f4946d85ad04c4; version=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <d208b89401e073de986dc891037c5a668f5d5d95; version=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <d29c78d3f9c5d2604548c1065bf1ec212728ea61; version=6a8736d10cb413be95ea443ba40f25c93f4ef9b2 <d35aef9c60d310eff3eaddacce301efe877e2b7c

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

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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