FITS GZIP decompression bomb in Pillow
### 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.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-40192US | high7.5 | — | ||
Pillow is a Python imaging library. Versions 10.3.0 through 12.1.1 did not limit the amount of GZIP-compressed data read when decoding a FITS image, making them vulnerable to decom… | ||||
references
External citations — patches, advisories, analysis.
- https://github.com/python-pillow/PillowPACKAGE
- https://github.com/python-pillow/Pillow/commit/3cb854e8b2bab43f40e342e665f9340d861aa628WEB
- https://github.com/python-pillow/Pillow/pull/9521WEB
- https://github.com/python-pillow/Pillow/security/advisories/GHSA-whj4-6x5x-4v2jWEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-40192ADVISORY
- https://pillow.readthedocs.io/en/stable/releasenotes/12.2.0.html#prevent-fits-decompression-bombWEB
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