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Fencer Vulns
high 7.8

CVE-2025-21879 json

btrfs: fix use-after-free on inode when scanning root during em shrinking

published 2025-03-27 19 mo ago modified 2026-08-05 3 mo ago also EUVD-2025-8487

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix use-after-free on inode when scanning root during em shrinking

At btrfs_scan_root() we are accessing the inode's root (and fs_info) in a call to btrfs_fs_closing() after we have scheduled the inode for a delayed iput, and that can result in a use-after-free on the inode in case the cleaner kthread does the iput before we dereference the inode in the call to btrfs_fs_closing().

Fix this by using the fs_info stored already in a local variable instead of doing inode->root->fs_info.

Patch / fix

  • Linux Linux 6.13.6, 6.14

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-21879 updated cvss 7.8

kernel: btrfs: fix use-after-free on inode when scanning root during em shrinking

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
19 mo ago

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CISA ADP 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.