CVE-2026-91186 json
PNG decoder: a duplicate IHDR chunk after IDAT resizes the image after allocation, causing a heap out-of-bounds write
published 2026-10-20 20 d ago modified 2026-10-20 19 d ago also EUVD-2026-105034
- cvss
- 8.4
- version 4.0, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 5%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- Eclipse Foundation Eclipse ThreadX - GUIX 6.5.2.202603
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 20 d ago
Exploit prediction
0.16% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.4 | CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N |
| CNA | 4.0 | 8.4 | CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected products
- Eclipse Foundation Eclipse ThreadX - GUIX
Classification
References
Sources
- CVE List CVE-2026-91186
- NVD CVE-2026-91186
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.