CVE-2025-21879

Inode use-after-free via delayed iput race

Published Mar 27, 2025 · Updated Aug 5, 2026

Use-after-free in Linux kernel 6.13 btrfs allows local users to trigger an invalid inode access during extent-map root scanning. In btrfs_scan_root(), a delayed iput can let the cleaner kthread free an inode before btrfs_fs_closing() dereferences inode->root->fs_info. A locally mounted btrfs filesystem and a low-privileged local account are required; the published record defines no deterministic consequence beyond the invalid kernel access.

CVSS severity7.8
High
EPSS probability0.20%
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 6.13 btrfs allows local users to trigger an invalid inode access during extent-map root scanning. In btrfs_scan_root(), a delayed iput can let the cleaner kthread free an inode before btrfs_fs_closing() dereferences inode->root->fs_info. A locally mounted btrfs filesystem and a low-privileged local account are required; the published record defines no deterministic consequence beyond the invalid kernel access.

The record

CVE
CVE-2025-21879
Published
Mar 27, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 27, 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=1020443840569535f6025a855958f07ea3eebf71 <59f37036bb7ab3d554c24abc856aabca01126414
  2. Affected versionversion=1020443840569535f6025a855958f07ea3eebf71 <5e79d26014f9386387575b9ed60d342057cee49b
  3. Affected versionversion=6.13
  4. Affected versionversion=fef55c4d9c9c22264d2b2ceae1e26922cb6129a5 <07836bc18f4ae42da4e922244f4685561c18755e

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1020443840569535f6025a855958f07ea3eebf71 <59f37036bb7ab3d554c24abc856aabca01126414; version=1020443840569535f6025a855958f07ea3eebf71 <5e79d26014f9386387575b9ed60d342057cee49b; version=6.13; version=fef55c4d9c9c22264d2b2ceae1e26922cb6129a5 <07836bc18f4ae42da4e922244f4685561c18755e

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free

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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