BREW-aider-CVE-2026-112896 — Pillow: TIFF encoder ColorMap plane-size mismatch causes a heap out-of-bounds read

Affected: Homebrew: aider

## Summary

A small attacker-supplied TIFF can be opened and loaded normally, then reach an out-of-bounds read when an application saves it back to TIFF with retained metadata. The fixed reproducer is a 1×1, 16-bit grayscale, PackBits-compressed TIFF containing tag 320 (ColorMap) with **768 SHORT values**: three zero-filled planes of 256 entries each. No Python object is forged and no metadata is injected after loading.

Pillow's TIFF encoder allocates **768 × 2 = 1536 bytes**, then passes three plane pointers separated by 256 SHORT entries to libtiff. With `BitsPerSample = 16`, libtiff instead expects **65536 SHORT values per plane** and attempts a **131072-byte read** from a plane pointer. Existing ASAN observations identify a heap-buffer-overflow READ crossing the 1536-byte allocation made in `PyImaging_LibTiffEncoderNew`.

The malformed ColorMap need not be a valid palette for this grayscale image. The issue is that accepted metadata is forwarded on save without reconciling the fixed plane extent with the effective sample depth. Opening/loading alone is not the demonstrated fault; the encoder path is required.

## Impact and prerequisites

An application must accept the input, retain the relevant TIFF metadata, and invoke the libtiff-backed TIFF save path. The observed consequence is an out-of-bounds read and ASAN termination. Process-memory exposure during encoding is a potential consequence, **not demonstrated by extracting arbitrary heap contents in this report**. No…

CVE-2026-112896 — Pillow: TIFF encoder ColorMap plane-size mismatch causes a heap out-of-bounds read

Affected: python-pillow Pillow

Pillow is a Python imaging library. Prior to 13.0.0, Pillow's TIFF encoder can read beyond a ColorMap buffer when retained TIFF metadata has a plane size inconsistent with BitsPerSample. A small TIFF can be opened normally and then retain a crafted ColorMap that is reused when the image is saved. An application that re-encodes the attacker's TIFF with libtiff can trigger the out-of-bounds read. This can disclose heap memory in the output or crash the process. This issue is fixed in version 13.0.0.

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BREW-aider-CVE-2026-112896 — Pillow: TIFF encoder ColorMap plane-size mismatch causes a heap out-of-bounds read

CVE-2026-112896 — Pillow: TIFF encoder ColorMap plane-size mismatch causes a heap out-of-bounds read