CVE-2026-91189
The GUIX binary resource loader never checks that a font page's glyph range is well formed.
Overview
CVE-2026-91189 is a known-severity vulnerability. It was published on October 20, 2026.
Technical description
The GUIX binary resource loader never checks that a font page's glyph range is well formed. `gx_page_header_first_glyph` and `gx_page_header_last_glyph` are read verbatim from the file and only the upper bound of `last_glyph` is validated, so a page declaring `first_glyph > last_glyph` makes `last - first + 1` underflow to a very large unsigned count.
That count is multiplied by a glyph record size to reserve the load buffer, and the multiply is unchecked, so it wraps to a small value and the loader allocates a buffer far smaller than the data it is about to write. The load pass then recomputes the count in a narrower type and writes attacker-controlled glyph records into the undersized buffer.
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.
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Frequently asked questions
What is CVE-2026-91189?
CVE-2026-91189 is a known-severity vulnerability. It was published on October 20, 2026.
How severe is CVE-2026-91189?
CVSS score information is not yet available for this vulnerability. Check back as the CVE record is updated by NVD analysts.
How do I fix or remediate CVE-2026-91189?
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-2026-91189?
CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-91189 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.