Package Instance

ImageMagick CLAHE : Unsigned underflow and division-by-zero lead to OOB pointer arithmetic and process crash (DoS)
A single root cause in the CLAHE implementation — tile width/height becoming zero — produces two distinct but related unsafe behaviors.
Vulnerabilities exists in the `CLAHEImage()` function of ImageMagick’s `MagickCore/enhance.c`.

1. Unsigned integer underflow → out-of-bounds pointer arithmetic (OOB): when `tile_info.height == 0`, the expression `tile_info.height - 1` (unsigned) wraps to a very large value; using that value in pointer arithmetic yields a huge offset and OOB memory access (leading to memory corruption, SIGSEGV, or resource exhaustion).
2. **Division/modulus by zero**: where code performs `... / tile_info.width` or `... % tile_info.height` without re-checking for zero, causing immediate division-by-zero crashes under sanitizers or `abort` at runtime.

Both behaviors are triggered by the same invalid tile condition (e.g., CLI exact `-clahe 0x0!` or automatic tile derivation `dim >> 3 == 0` for very small images).

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