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CVE-2025-21879

7.8 · HIGH

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 roo…

Published Mar 27, 2025CWE-416EPSS 0.20%

Overview

CVE-2025-21879 is a high-severity vulnerability. It was published on March 27, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/07836bc18f4ae42da4e922244f4685561c18755eRefgit.kernel.org/stable/c/59f37036bb7ab3d554c24abc856aabca01126414Refgit.kernel.org/stable/c/5e79d26014f9386387575b9ed60d342057cee49b

How CyberStrike helps

Frequently asked questions

What is CVE-2025-21879?

CVE-2025-21879 is a high-severity vulnerability. It was published on March 27, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-21879?

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2025-21879?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-21879?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-21879 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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