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CVE-2026-90203

7.1 · HIGH

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 decompresse…

Published Sep 17, 2026EPSS 0.17%

Overview

CVE-2026-90203 is a high-severity vulnerability. It was published on September 17, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/3d2f0cb66c909ea2312cdef465165bb9a3ba2d84Refgit.kernel.org/stable/c/95dadf366c117dcdca78a570e6832071deab1ecdRefgit.kernel.org/stable/c/b169185d5c672b989985c6c2e38cafab2548ba88Refgit.kernel.org/stable/c/bbb2218eb072b0a15dc063929200183bd23c2344Refgit.kernel.org/stable/c/c2a126fca820ae74872da28de68dc74d4595dc4bRefgit.kernel.org/stable/c/d0a3729d464fcf516416a41cf304c0c92126ee03Refgit.kernel.org/stable/c/e300eb5002925b29be803d2661af07266cfa267eRefgit.kernel.org/stable/c/e4afd90bc7bf3dd477970c6c42bdd29ad3fda7fe

How CyberStrike helps

Frequently asked questions

What is CVE-2026-90203?

CVE-2026-90203 is a high-severity vulnerability. It was published on September 17, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

How severe is CVE-2026-90203?

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-90203?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-90203?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-90203 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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