Pillow: Heap buffer overflow in FlashPix (FPX) JPEG decoding leads to code execution

Why it is Amber

• CVSS 9.2 critical
• Remotely exploitable without logging in
• On your watchlist: PyPI

Affected packages

References

• https://github.com/python-pillow/Pillow/commit/242a059aedc1935097d9aa1dc3f099750467ba75
• https://github.com/python-pillow/Pillow/releases/tag/13.0.0
• https://github.com/python-pillow/Pillow/security/advisories/GHSA-5x8w-8jj5-q52h
• https://github.com/python-pillow/Pillow/security/advisories/GHSA-5x8w-8jj5-q52h
• https://github.com/advisories/GHSA-5x8w-8jj5-q52h
• https://nvd.nist.gov/vuln/detail/CVE-2026-112398
• https://github.com/advisories/GHSA-5x8w-8jj5-q52h

Original description

Pillow is a Python imaging library. Prior to 13.0.0, Pillow's FlashPix JPEG-tile decoder can write decoded scanlines beyond the allocated tile buffer. FlashPix (FPX) JPEG decoding selects raw mode LA with two bytes per pixel, while an unrecognized JPEG mode can be decoded as JCS_UNKNOWN with four components, causing ImagingJpegDecode to write four-component scanlines into the two-byte tile buffer. An attacker can supply a crafted OLE2 FlashPix file to an application with the optional olefile dependency installed that opens or thumbnails untrusted input. This can corrupt heap memory and may allow arbitrary code execution. This issue is fixed in version 13.0.0.