CVE-2025-38415

medium

Published 2026-02-09 · Modified 2026-02-02

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CVSS v3

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CVSS v4 NEW

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not yet in upstream

VIR risk

5.5

Description

In the Linux kernel, the following vulnerability has been resolved: Squashfs: check return result of sb_min_blocksize Syzkaller reports an "UBSAN: shift-out-of-bounds in squashfs_bio_read" bug. Syzkaller forks multiple processes which after mounting the Squashfs filesystem, issues an ioctl("/dev/loop0", LOOP_SET_BLOCK_SIZE, 0x8000). Now if this ioctl occurs at the same time another process is in the process of mounting a Squashfs filesystem on /dev/loop0, the failure occurs. When this happens the following code in squashfs_fill_super() fails. ---- msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE); msblk->devblksize_log2 = ffz(~msblk->devblksize); ---- sb_min_blocksize() returns 0, which means msblk->devblksize is set to 0. As a result, ffz(~msblk->devblksize) returns 64, and msblk->devblksize_log2 is set to 64. This subsequently causes the UBSAN: shift-out-of-bounds in fs/squashfs/block.c:195:36 shift exponent 64 is too large for 64-bit type 'u64' (aka 'unsigned long long') This commit adds a check for a 0 return by sb_min_blocksize().

Predictions

Exploit likelihood

20%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

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OS impact

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

AlmaLinux Fixed 1 release

Version	Status	Fixed in
9	Fixed	`kernel-64k-devel-5.14.0-611.30.1.el9_7.aarch64.rpm`

Debian Fixed 5 releases

Version	Status	Fixed in
trixie	Fixed	`6.12.35-1`
sid	Fixed	`6.12.35-1`
forky	Fixed	`6.12.35-1`
bullseye	Fixed	`5.10.244-1`
bookworm	Fixed	`6.1.147-1`

Red Hat Fixed 2 releases

Version	Status	Fixed in
9	Fixed	—
8	Fixed	—

Rocky Linux Fixed 2 releases

Version	Status	Fixed in
9	Fixed	—
8	Fixed	—

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.