Pillow, a popular Python imaging library, constructs a combined bitmap of individual glyphs when compiling a font. In versions before 12.3.0 this routine calls Image.new("1", (xsize, ysize)) without invoking the internal decompression bomb check. A maliciously crafted font can therefore cause the library to allocate an enormous amount of memory, leading to process crashes or resource exhaustion. The flaw is catalogued as CWE‑1050 and CWE‑789 and results in a denial of service whenever a vulnerable Pillow installation processes a compromised font file.

Any software that incorporates Pillow older than version 12.3.0 is at risk. This includes web applications, desktop utilities, data pipelines, and any service that accepts or renders fonts from external sources. All platforms—Linux, Windows, macOS—running an unpatched Pillow installation could be affected.

The CVSS score of 7.5 indicates moderate to high severity while the EPSS score of < 1% suggests a very low but nonzero likelihood of exploitation at the time of analysis. The vulnerability is not listed in CISA’s KEV catalog. Exploitation requires that the attacker or a third‑party provides a maliciously malformed font file to the application. The likely attack vectors are local—where a user uploads a harmful font—or remote—where a web or service component loads untrusted font data, resulting in a denial of service of the Pillow process and any dependent functionality.