CVE WatchOct 20, 2026

CVE-2026-91186

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 trans

CVSS

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No CVSS

EPSS

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KEV

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Exploit Today

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0-100

Published: Oct 20, 2026 · Last modified: Oct 20, 2026 · CWE-125 · CWE-787

EPSS · 30d

Not enough EPSS history yet.

Technical 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.

Official references

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

Related CVEs

CVECVSSEPSSKEVRExploitTitleMod.

CVE-2026-96402—

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———A malicious USB MTP/PTP device can cause the USBX host to read past a heap buffer during ordinary object enumeration, leaking adjacent heap contents to the application or faulting on an unmapped page.2h CVE-2026-95111—

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———A memory-protected ThreadX module's queue request reaches the Module Manager's dispatch layer, which decides how much of the module's buffer the privileged queue copy may touch and hands that extent to the module port's range check. A queue's `tx_queue_message_size` is a count of `ULONG`s and the copy moves that many words, so the extent is `message_size * sizeof(ULONG)` bytes. The front-send dispatcher passed the word count itself. `tx_queue_send` and `tx_queue_receive`, either side of it in the same header, have always multiplied. A source buffer ending `message_size` bytes into memory the module may read was therefore accepted, and `_txe_queue_front_send` then read `message_size * sizeof(ULONG)` bytes from it in privileged mode — `3 * message_size` bytes past the end of what the module is allowed to read. The words are written into the queue's message area, so a module that can receive from that queue reads them back.2h CVE-2026-924546.1 MED

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———The GUIX software JPEG decoder reads four kinds of marker segment without checking that each is long enough to hold what it reads. A truncated segment is therefore read past the end of the caller's image buffer. Separately, a zero chroma sampling factor makes the block decode loop non-terminating. Both reproduce in the default configuration, in which `GX_SOFTWARE_DECODER_SUPPORT` is enabled.2h CVE-2026-92449—

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———`_gx_binres_pixelmap_table_load()` in the GUIX binary resource (theme) loader indexes the pixelmap table with a value read verbatim from the resource file and never bounds it against the table size. A crafted theme drives a write of up to roughly 256 KB past the end of the table. The overflowed buffer is allocated by GUIX itself, through `_gx_system_memory_allocator`, rather than supplied by the caller, so the loader corrupts its own arena. The public API `gx_binres_theme_load()` takes no size parameter, so no amount of caller diligence prevents this. Reproduces in the shipped default configuration; `GX_BINARY_RESOURCE_SUPPORT` is enabled by default.2h CVE-2026-92446—

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———`gx_binres_theme_load()` and `gx_binres_font_load()` take the resource as a bare `GX_UBYTE *` with no length, and `GX_BINRES_DATA_INFO` has no field to carry one. Every read is therefore performed at an offset the file itself chose, against a buffer whose extent the loader does not know. A resource that declares more data than it contains is read past its end, and an offset stored in the file is turned into a pointer without being bounded. This is a distinct defect from GHSA-hgcj-22cg-4hfv, which was an underflowed glyph count. It needs no underflow and no wrapped multiply: a perfectly well-formed, narrow glyph range reaches it.2h CVE-2026-91189—

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———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.2h