CVE-2026-90203In 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.