An out-of-bounds write vulnerability exists in the Grassroots DICOM library (GDCM). The issue is triggered during parsing of a malformed DICOM file containing encapsulated PixelData fragments (compressed image data stored as multiple fragments). This vulnerability leads to a segmentation fault caused by an out-of-bounds memory access due to unsigned integer underflow in buffer indexing. It is exploitable via file input, simply opening a crafted malicious DICOM file is sufficient to trigger the crash, resulting in a denial-of-service condition.