CVE-2021-47340

Kernel crash via null ipimap dereference

Published May 21, 2024 · Updated May 11, 2026

NULL pointer dereference in Linux JFS allows local users to crash the kernel by reaching JFS inode eviction on affected systems. During jfs_evict_inode, the code calls diFree when JFS_SBI(inode->i_sb)->ipimap is NULL, causing JFS_IP to derive an invalid pointer before reading i_imap. Exploitation requires local low-privileged access and a JFS inode eviction in this invalid state; the bounded consequence is an availability-only kernel crash.

CVSS severity5.5
Medium
EPSS probability0.26%
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 Linux JFS allows local users to crash the kernel by reaching JFS inode eviction on affected systems. During jfs_evict_inode, the code calls diFree when JFS_SBI(inode->i_sb)->ipimap is NULL, causing JFS_IP to derive an invalid pointer before reading i_imap. Exploitation requires local low-privileged access and a JFS inode eviction in this invalid state; the bounded consequence is an availability-only kernel crash.

The record

CVE
CVE-2021-47340
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 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=2.6.36
  2. Affected versionversion=62aff86fdf18657d9eca7878654415f94f16d027 <3bb27e27240289b47d3466f647a55c567adbdc3a
  3. Affected versionversion=62aff86fdf18657d9eca7878654415f94f16d027 <42f102ea1943ecb10a0756bf75424de5d1d5beed
  4. Affected versionversion=62aff86fdf18657d9eca7878654415f94f16d027 <49def1b0644892e3b113673c13d650c3060b43bc
  5. Affected versionversion=62aff86fdf18657d9eca7878654415f94f16d027 <745c9a59422c63f661f4374ed5181740db4130a1
  6. Affected versionversion=62aff86fdf18657d9eca7878654415f94f16d027 <7bde24bde490f3139eee147efc6d60d6040fe975
  7. Affected versionversion=62aff86fdf18657d9eca7878654415f94f16d027 <8018936950360f1c503bb385e158cfc5e4945d18
  8. Affected versionversion=62aff86fdf18657d9eca7878654415f94f16d027 <9d574f985fe33efd6911f4d752de6f485a1ea732
  9. Affected versionversion=62aff86fdf18657d9eca7878654415f94f16d027 <a21e5cb1a64c904f1f0ef7b2d386fc7d2b1d2ce2
  10. Affected versionversion=62aff86fdf18657d9eca7878654415f94f16d027 <aff8d95b69051d0cf4acc3d91f22299fdbb9dfb3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.36; version=62aff86fdf18657d9eca7878654415f94f16d027 <3bb27e27240289b47d3466f647a55c567adbdc3a; version=62aff86fdf18657d9eca7878654415f94f16d027 <42f102ea1943ecb10a0756bf75424de5d1d5beed; version=62aff86fdf18657d9eca7878654415f94f16d027 <49def1b0644892e3b113673c13d650c3060b43bc; version=62aff86fdf18657d9eca7878654415f94f16d027 <745c9a59422c63f661f4374ed5181740db4130a1; version=62aff86fdf18657d9eca7878654415f94f16d027 <7bde24bde490f3139eee147efc6d60d6040fe975; version=62aff86fdf18657d9eca7878654415f94f16d027 <8018936950360f1c503bb385e158cfc5e4945d18; version=62aff86fdf18657d9eca7878654415f94f16d027 <9d574f985fe33efd6911f4d752de6f485a1ea732; version=62aff86fdf18657d9eca7878654415f94f16d027 <a21e5cb1a64c904f1f0ef7b2d386fc7d2b1d2ce2; version=62aff86fdf18657d9eca7878654415f94f16d027 <aff8d95b69051d0cf4acc3d91f22299fdbb9dfb3

Published CVSS scores

5.5NIST NVDCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
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.

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Technologies

Your stack

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Your stack

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