CVE-2021-47493

Kernel panic via unsynchronized journal-head release

Published May 22, 2024 · Updated Aug 5, 2026

Race condition in Linux kernel OCFS2 allows local users to trigger a kernel panic during file writes on an affected OCFS2 volume. ocfs2_test_bg_bit_allocatable calls bh2jh on a buffer_head while jbd2_journal_put_journal_head can concurrently clear its b_private journal_head pointer. Concurrent OCFS2 allocation and journal-head release can therefore dereference the null pointer and produce a kernel page fault and panic.

CVSS severity4.7
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Linux kernel OCFS2 allows local users to trigger a kernel panic during file writes on an affected OCFS2 volume. ocfs2_test_bg_bit_allocatable calls bh2jh on a buffer_head while jbd2_journal_put_journal_head can concurrently clear its b_private journal_head pointer. Concurrent OCFS2 allocation and journal-head release can therefore dereference the null pointer and produce a kernel page fault and panic.

The record

CVE
CVE-2021-47493
Published
May 22, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-362, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 22, 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

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=2.6.16
  2. Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <2e382600e8856ea654677b5134ee66e03ea72bc2
  3. Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <5043fbd294f5909a080ade0f04b70a4da9e122b7
  4. Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <6f1b228529ae49b0f85ab89bcdb6c365df401558

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.16; version=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <2e382600e8856ea654677b5134ee66e03ea72bc2; version=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <5043fbd294f5909a080ade0f04b70a4da9e122b7; version=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <6f1b228529ae49b0f85ab89bcdb6c365df401558

Published CVSS scores

4.7UbuntuCVSS:3.1/AV:L/AC:H/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 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-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Endpoint Denial of Service: Application 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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