# CVE-2026-91186: Eclipse ThreadX GUIX PNG decoder heap overflow on duplicate IHDR

Source: https://junglewise.ai/threats/cve-2026-91186-the-png-chunk-reader-has-no-notion-of-chunk-ordering-it-records  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-20. Updated: 2026-10-20  
License: CC BY 4.0 with a link back

CVE-2026-91186 · Severity: info · Published 2026-10-20

Eclipse ThreadX GUIX is an embedded GUI framework that decodes PNG images by default. A maliciously crafted PNG file can trigger a heap buffer overflow by placing a second image header (IHDR) chunk after image data (IDAT), causing the decoder to write image data beyond the allocated buffer boundary. This could corrupt adjacent memory or crash applications on embedded systems.

Technologies: [Eclipse ThreadX GUIX](https://junglewise.ai/threats/technologies/guix). Vendors: [Eclipse ThreadX](https://junglewise.ai/threats/vendors/eclipse-threadx).

## Quick answers

**Is CVE-2026-91186 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-91186 being exploited in the wild.

**How severe is CVE-2026-91186?** Informational severity, published 20 October 2026.

**Which products and versions are affected?** Eclipse ThreadX GUIX 6.5.1.202602a and earlier.

**Is there a fix for CVE-2026-91186?** Yes: fixed in 6.5.2.202603. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-91186 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-91186?** Check whether you run Eclipse ThreadX GUIX at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 6.5.2.202603

## Technical details

The PNG decoder does not validate chunk ordering and allows a duplicate IHDR chunk to be processed after IDAT. The second IHDR redefines image dimensions after the decode buffer has already been allocated based on the first header's dimensions. The unfilter pass then uses the new dimensions to iterate over the buffer, writing beyond its bounds via memmove with attacker-controlled extent. The vulnerability is reachable via the public API with a specially crafted PNG file and no user interaction required.

## Affected products

- Eclipse ThreadX GUIX 6.5.1.202602a and earlier

## Timeline

- 2026-10-02: disclosed
- 2026-10-20: advisory

## References

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

## Related threats

- [Eclipse ThreadX GUIX multi-line text view out-of-bounds read](https://junglewise.ai/threats/cve-2026-91057-gx-multi-line-text-view-display-info-get-reads-one-byte-past-the)
- [GUIX JPEG decoder buffer over-read and infinite loop](https://junglewise.ai/threats/cve-2026-92454-the-guix-software-jpeg-decoder-reads-four-kinds-of-marker-segment)
- [Eclipse ThreadX GUIX binary resource heap buffer overflow](https://junglewise.ai/threats/cve-2026-92449-gx-binres-pixelmap-table-load-in-the-guix-binary-resource-theme)
- [Eclipse ThreadX GUIX binary resource loader out-of-bounds read](https://junglewise.ai/threats/cve-2026-92446-gx-binres-theme-load-and-gx-binres-font-load-take-the-resource-as)
- [Eclipse ThreadX GUIX binary resource loader integer underflow in font parsing](https://junglewise.ai/threats/cve-2026-91189-the-guix-binary-resource-loader-never-checks-that-a-font-page-s)