TI-2026-76831 Aliases CVE-2026-91189

Integer underflow in Eclipse ThreadX GUIX font loader enables heap overflow

LOW 32CWE-190Published 2026-10-20 · Updated 2026-10-20

Key facts

Attack vector: Local
Privileges required: None
User interaction: Active
Attack complexity: High
Attack requirements: None
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-190 and the CVSS impact.

Summary

Eclipse ThreadX GUIX, from 0 through 6.5.1.202602a, is affected. The GUIX binary resource loader never checks that a font page's glyph range is well formed, so a page with first_glyph greater than last_glyph makes the glyph count underflow. The unchecked size multiplication wraps to a small value, so the loader allocates a buffer too small for the glyph records it writes, a heap out-of-bounds write (CWE-787). A local attacker needs no privileges, but exploitation requires a user to load an untrusted font or theme file and needs user interaction.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00135 2nd percentileScored 2026-11-07

Fix Fixed Eclipse ThreadX - GUIX (Eclipse Foundation): 6.5.2.202603

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Eclipse Foundation	Eclipse ThreadX - GUIX	up to 6.5.1.202602a	6.5.2.202603	Patch available	CNA

Eclipse ThreadX - GUIX VendorEclipse Foundation Affected up to 6.5.1.202602a Fixed in 6.5.2.202603 Patch available CNA

Remediation

Update Eclipse ThreadX GUIX to 6.5.2.202603 or later, which fixes the flaw. The sources list no advisory identifier for this fix.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Fix · CNA Eclipse ThreadX - GUIX (Eclipse Foundation) Fixed in 6.5.2.202603

Timeline

2026-10-20 Threatist record created from CVE-2026-91189

References

Other 1

https://github.com/eclipse-threadx/guix/security/advisories/GHSA-hgcj-22cg-4hfv

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Sources

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