What’s Vulnerable › Vulnerabilities

CVE-2026-90203: Squashfs: check block offset is not negative

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-17 · updated 2026-10-19

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.

Affected products

• Linux kernel: 2.6.29 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux kernel 7.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/3d2f0cb66c909ea2312cdef465165bb9a3ba2d84
• https://git.kernel.org/stable/c/95dadf366c117dcdca78a570e6832071deab1ecd
• https://git.kernel.org/stable/c/b169185d5c672b989985c6c2e38cafab2548ba88
• https://git.kernel.org/stable/c/bbb2218eb072b0a15dc063929200183bd23c2344
• https://git.kernel.org/stable/c/c2a126fca820ae74872da28de68dc74d4595dc4b
• https://git.kernel.org/stable/c/d0a3729d464fcf516416a41cf304c0c92126ee03
• https://git.kernel.org/stable/c/e300eb5002925b29be803d2661af07266cfa267e
• https://git.kernel.org/stable/c/e4afd90bc7bf3dd477970c6c42bdd29ad3fda7fe

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