CVE-2026-96637: python-pillow pillow Uncontrolled Resource Consumption

Vulnerability summary

CVE-2026-96637 is a high (CVSS 7.1) Uncontrolled Resource Consumption vulnerability in python-pillow pillow.

Timeline

1. 21-10-2026
   PublishedVulnerability first disclosed.

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.

• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
• CWE-409Improper Handling of Highly Compressed Data (Data Amplification)The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.