Vulnerability record · CVE-2026-90203 · published 17 September 2026
CVE-2026-90203: In the Linux kernel, the following vulnerability has been resolved: Squashfs: check block offset is not negat…
In the Linux kernel, the following vulnerability has been resolved: Squashfs: check block offset is not negative If a negative offset is read off disk (for example the offset into the decompressed fragment block), this will cause squashfs_copy_data() to perform an out of bounds access. Fix by checking if offset is negative, and returning 0. This matches existing behaviour where an offset beyond the block returns 0 bytes copied. To trigger this out of bounds access requires a crafted Squashfs filesystem and CAP_SYS_ADMIN to mount it. Unprivileged users will not be able to mount such a filesystem, but once mounted, an unprivileged user can trigger the out of bounds access by reading the crafted file with the negative offset.
Description
In the Linux kernel, the following vulnerability has been resolved: Squashfs: check block offset is not negative If a negative offset is read off disk (for example the offset into the decompressed fragment block), this will cause squashfs_copy_data() to perform an out of bounds access. Fix by checking if offset is negative, and returning 0. This matches existing behaviour where an offset beyond the block returns 0 bytes copied. To trigger this out of bounds access requires a crafted Squashfs filesystem and CAP_SYS_ADMIN to mount it. Unprivileged users will not be able to mount such a filesystem, but once mounted, an unprivileged user can trigger the out of bounds access by reading the crafted file with the negative offset.
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
References
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Source: NIST National Vulnerability Database (record CVE-2026-90203), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.
