CVE-2026-96642

Pillow: TarIO negative size field causes infinite CPU-spin loop

Description

Pillow is a Python imaging library. Prior to 13.0.0, the TarIO initializer in src/PIL/TarIO.py accepts a negative octal member size and computes a backward seek that returns to the same 512-byte header. When the requested member name does not match, the parser repeatedly reads that header, consumes a full CPU core, and never returns. TarIO is reached only when an application directly uses PIL.TarIO.TarIO rather than the default Image.open() path. This issue is fixed in version 13.0.0.

Scores

Weaknesses (CWE)

• CWE-835

Advisories

• GHSA-3j72-p6qg-6xp7 — Pillow: TarIO negative size field causes infinite CPU-spin loop
• PYSEC-2026-4341 — Pillow is a Python imaging library. Prior to 13.0.0, the TarIO initializer in src/PIL/TarIO.py accepts a negative octal member size and computes a backward seek

European references

• ENISA EUVD · EUVD-2026-107561
• GCVE · GCVE-0-2026-96642

Affected configurations (NVD CPE)

• cpe:2.3:a:python:pillow:*:*:*:*:*:*:*:* < 13.0.0

Affected products

References

• https://github.com/python-pillow/Pillow/security/advisories/GHSA-3j72-p6qg-6xp7
• https://github.com/python-pillow/Pillow/pull/10012
• https://github.com/python-pillow/Pillow/commit/19b695fdcc5eddc37374e2b1645fc4185edaf71d
• https://github.com/python-pillow/Pillow/releases/tag/13.0.0

Sources