Heap buffer overflow with attacker-controlled data in XBM parser

ImageMagick is free and open-source software used for editing and manipulating digital images. Prior to versions 7.1.2-13 and 6.9.13-38, a heap buffer overflow vulnerability in the XBM image decoder (ReadXBMImage) allows an attacker to write controlled data past the allocated heap buffer when processing a maliciously crafted image file. Any operation that reads or identifies an image can trigger the overflow, making it exploitable via common image upload and processing pipelines. Versions 7.1.2-13 and 6.9.13-38 fix the issue.