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.
Metrics
Affected Vendors & Products
References
History
Wed, 21 Oct 2026 17:15:00 +0000
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Eclipse
Eclipse threadx Guix |
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| Vendors & Products |
Eclipse
Eclipse threadx Guix |
Tue, 20 Oct 2026 16:30:00 +0000
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ssvc
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Tue, 20 Oct 2026 15:00:00 +0000
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| Description | 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. | |
| Title | PNG decoder: a duplicate IHDR chunk after IDAT resizes the image after allocation, causing a heap out-of-bounds write | |
| Weaknesses | CWE-125 CWE-787 |
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| References |
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| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: eclipse
Published: 2026-10-20T14:47:52.216Z
Updated: 2026-10-20T15:28:59.237Z
Reserved: 2026-09-23T13:43:04.337Z
Link: CVE-2026-91186
Updated: 2026-10-20T15:28:54.853Z
Status : Awaiting Analysis
Published: 2026-10-20T15:17:36.023
Modified: 2026-10-20T19:48:50.250
Link: CVE-2026-91186
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