CVE-2021-47656

Kernel memory corruption via double-cleared JFFS2 xattrs

Published Feb 26, 2025 · Updated Aug 5, 2026

Use-after-free in Linux kernel JFFS2 starting in 2.6.18 allows context-dependent attackers to corrupt kernel memory via a crafted image. After a scan error, jffs2_clear_xattr_subsystem frees xattr references during filesystem construction, then jffs2_do_fill_super calls it again and reads the freed list. A privileged victim process must mount the attacker-supplied image; the double clear can panic the kernel or corrupt kernel memory.

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

Use-after-free in Linux kernel JFFS2 starting in 2.6.18 allows context-dependent attackers to corrupt kernel memory via a crafted image. After a scan error, jffs2_clear_xattr_subsystem frees xattr references during filesystem construction, then jffs2_do_fill_super calls it again and reads the freed list. A privileged victim process must mount the attacker-supplied image; the double clear can panic the kernel or corrupt kernel memory.

The record

CVE
CVE-2021-47656
Published
Feb 26, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 26, 2025CVE 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

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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=2.6.18
  2. Affected versionversion=aa98d7cf59b5b0764d3502662053489585faf2fe <22327bd7988f21de3a53c1373f3b81542bfe1f44
  3. Affected versionversion=aa98d7cf59b5b0764d3502662053489585faf2fe <30bf7244acf32f19cb722c39f7bc1c2a9f300422
  4. Affected versionversion=aa98d7cf59b5b0764d3502662053489585faf2fe <3bd2454162ec6bbb5503233c804fce6e4b6dcec5
  5. Affected versionversion=aa98d7cf59b5b0764d3502662053489585faf2fe <4c7c44ee1650677fbe89d86edbad9497b7679b5c
  6. Affected versionversion=aa98d7cf59b5b0764d3502662053489585faf2fe <7a75740206af5f17e9f3efa384211cba70213da1
  7. Affected versionversion=aa98d7cf59b5b0764d3502662053489585faf2fe <7bb7428dd73991bf4b3a7a61b493ca50046c2b13
  8. Affected versionversion=aa98d7cf59b5b0764d3502662053489585faf2fe <8c0f024f29e055840a5a89fe23b96ae3f921afed
  9. Affected versionversion=aa98d7cf59b5b0764d3502662053489585faf2fe <9150cb625b46f68d524f4cfd491f1aafc23e10a9
  10. Affected versionversion=aa98d7cf59b5b0764d3502662053489585faf2fe <c3b07c875fa8f906f932976460fd14798596f101

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.18; version=aa98d7cf59b5b0764d3502662053489585faf2fe <22327bd7988f21de3a53c1373f3b81542bfe1f44; version=aa98d7cf59b5b0764d3502662053489585faf2fe <30bf7244acf32f19cb722c39f7bc1c2a9f300422; version=aa98d7cf59b5b0764d3502662053489585faf2fe <3bd2454162ec6bbb5503233c804fce6e4b6dcec5; version=aa98d7cf59b5b0764d3502662053489585faf2fe <4c7c44ee1650677fbe89d86edbad9497b7679b5c; version=aa98d7cf59b5b0764d3502662053489585faf2fe <7a75740206af5f17e9f3efa384211cba70213da1; version=aa98d7cf59b5b0764d3502662053489585faf2fe <7bb7428dd73991bf4b3a7a61b493ca50046c2b13; version=aa98d7cf59b5b0764d3502662053489585faf2fe <8c0f024f29e055840a5a89fe23b96ae3f921afed; version=aa98d7cf59b5b0764d3502662053489585faf2fe <9150cb625b46f68d524f4cfd491f1aafc23e10a9; version=aa98d7cf59b5b0764d3502662053489585faf2fe <c3b07c875fa8f906f932976460fd14798596f101

Published CVSS scores

7.8CISA-ADPCVSS: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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1204.002User Execution: Malicious File

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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