CVE Catalog

CVE-2025-38709

MediumCVSS 5.5
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.15%

4th percentile - higher than 4% of all known CVEs

Summary

In the Linux kernel, a flaw was fixed in the loop driver where the block size of a loop device could be changed underneath a mounted filesystem. This caused a mismatch between the block device block size and the superblock block size, leading to confusion in places like fs/buffer.c. The fix acquires exclusive ownership of the loop device before changing its block size.

Risk Assessment

May lead to system instability, kernel warnings, and potential filesystem operation errors, affecting availability and data integrity.

Recommendation

Update the Linux kernel to a version containing the fix. Avoid changing the block size of loop devices in use by mounted filesystems.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: loop: Avoid updating block size under exclusive owner Syzbot came up with a reproducer where a loop device block size is changed underneath a mounted filesystem. This causes a mismatch between the block device block size and the block size stored in the superblock causing confusion in various places such as fs/buffer.c. The particular issue triggered by syzbot was a warning in __getblk_slow() due to requested buffer size not matching block device block size. Fix the problem by getting exclusive hold of the loop device to change its block size. This fails if somebody (such as filesystem) has already an exclusive ownership of the block device and thus prevents modifying the loop device under some exclusive owner which doesn't expect it.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS