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.
Published: 2026-10-20
Score: 7.1 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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History

Tue, 20 Oct 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Tue, 20 Oct 2026 15:00:00 +0000

Type Values Removed Values Added
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.
Title GUIX binary resource loader: unvalidated glyph range causes an integer underflow and a heap out-of-bounds write when loading an untrusted font or theme
Weaknesses CWE-190
CWE-680
CWE-787
References
Metrics cvssV4_0

{'score': 7.1, 'vector': 'CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'}

Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: eclipse

Published:

Updated: 2026-10-20T15:25:24.066Z

Reserved: 2026-09-23T13:43:04.319Z

Link: CVE-2026-91189

cve-icon Vulnrichment

Updated: 2026-10-20T15:25:19.259Z

cve-icon NVD

Status : Received

Published: 2026-10-20T15:17:36.167

Modified: 2026-10-20T16:17:16.600

Link: CVE-2026-91189

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses
  • CWE-190

    Integer Overflow or Wraparound

  • CWE-680

    Integer Overflow to Buffer Overflow

  • CWE-787

    Out-of-bounds Write