[ CVE-2026-96637 · Published 21 Oct 2026 ]

Pillow: Decompression bomb check bypass in SpiderImagePlugin.seek() leads to unbounded allocation DoS

CVSS 7.1 EPSS <1%Fix available

[ Description ]Official description

Pillow is a Python imaging library. Prior to 13.0.0, SpiderImageFile.seek() in src/PIL/SpiderImagePlugin.py reparses a later SPIDER stack frame and replaces self._size without rerunning Image._decompression_bomb_check(). A tiny file can use a safe first frame to pass Image.open() and then declare very large dimensions in a later mode F frame. Loading that frame allocates approximately four bytes per attacker-declared pixel and can consume multiple gigabytes of memory. This issue is fixed in version 13.0.0.

[ Fixes ]Fixes and patches

  • pillow 13.0.0Fixed version · GitHub Advisories · pip package pillow: upgrade to 13.0.0 or later (affected < 13.0.0)

[ Packages ]Affected open-source packages