TI-2026-76830 Aliases CVE-2026-91186

GUIX PNG decoder heap out-of-bounds write via duplicate IHDR chunk

LOW 38CWE-125Published 2026-10-20 · Updated 2026-10-20

Key facts

Attack vector: Local
Privileges required: None
User interaction: Active
Attack complexity: Low
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-787 and the CVSS impact.

Summary

The PNG decoder in Eclipse ThreadX GUIX does not check chunk ordering, so a second IHDR chunk placed after IDAT is accepted. It rewrites the image width, height, bit depth and pixel depth after the decoded-data buffer is allocated and filled, and the row-filter pass then reads and writes past the end of that buffer. GUIX allocates the buffer itself and the decoder is compiled in by default, so applications cannot size the buffer defensively. CVE-2026-91186 is rated CVSS 4.0 8.4 HIGH and is mapped to CWE-125 and CWE-787; it is not listed in CISA KEV.

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

Description from the CNA

The PNG chunk reader has no notion of chunk ordering. It records whether an IDAT has been seen and whether a tRNS has already supplied transparency, but nothing prevents an IHDR being read a second time. A PNG carries exactly one IHDR and it is the first chunk. A file that places a second one after IDAT rewrites the image width, height, bit depth and pixel depth *after* the decoded-data buffer has already been allocated and filled from the original values. The pass that reverses the PNG row filters then derives its own extent from the new dimensions and walks the old allocation, moving image bytes past the end of it. The buffer is allocated by GUIX rather than supplied by the caller, so the application has no way to size it defensively. The decoder is compiled in by default.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00159 5th 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

Upgrade Eclipse ThreadX GUIX to 6.5.2.202603, the fixed release. Versions from 0 through 6.5.1.202602a are affected.

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-2026-91186

References

Other 1

https://github.com/eclipse-threadx/guix/security/advisories/GHSA-gx8f-4rpc-4fjw

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TI-2026-13216 CWE-863: ABAC authorization bypass via trailing slash route normalization in Eclipse BaSyx Go Components CVSS 3.1CRITICAL 9.8
TI-2026-06514 Path traversal in Eclipse BaSyx CVSS 3.1CRITICAL 10.0
TI-2026-01382 In the Eclipse Theia Website repository, the GitHub Actions workflow… CVSS 3.1CRITICAL 10.0
TI-2026-74697 Authentication bypass in Eclipse Jetty EthereumAuthenticator CVSS 4.0CRITICAL 9.3

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Sources

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