HIGH 7.5

GHSA-whj4-6x5x-4v2j

FITS GZIP decompression bomb in Pillow

Details

### Impact Pillow did not limit the amount of GZIP-compressed data read when decoding a FITS image, making it vulnerable to decompression bomb attacks. A specially crafted FITS file could cause unbounded memory consumption, leading to denial of service (OOM crash or severe performance degradation).

### Patches The amount of data read is now limited to the necessary amount. Fixed in Pillow 12.2.0 (PR #9521).

### Workarounds Avoid Pillow >= 10.3.0, < 12.2.0 Only open [specific image formats](https://pillow.readthedocs.io/en/stable/releasenotes/8.0.0.html#image-open-add-formats-parameter), excluding FITS.

Are you affected?

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Affected packages

PyPI / pillow

Introduced in: 10.3.0 Fixed in: 12.2.0

Fix pip install --upgrade 'pillow>=12.2.0'

References

https://github.com/python-pillow/Pillow/security/advisories/GHSA-whj4-6x5x-4v2j [WEB]
https://nvd.nist.gov/vuln/detail/CVE-2026-40192 [ADVISORY]
https://github.com/python-pillow/Pillow/pull/9521 [WEB]
https://github.com/python-pillow/Pillow/commit/3cb854e8b2bab43f40e342e665f9340d861aa628 [WEB]
https://github.com/python-pillow/Pillow [PACKAGE]
https://pillow.readthedocs.io/en/stable/releasenotes/12.2.0.html#prevent-fits-decompression-bomb [WEB]