# FITS GZIP decompression bomb in Pillow

Advisory record · `GHSA-whj4-6x5x-4v2j`

- **Identifiers:** `GHSA-whj4-6x5x-4v2j` · `BIT-pillow-2026-40192` · `CVE-2026-40192` · `PYSEC-2026-2250`
- **State:** Confirmed
- **Severity:** CVSS 8.7 High
- **Critical:** No
- **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-409](https://cwe.mitre.org/data/definitions/409.html) · [CWE-770](https://cwe.mitre.org/data/definitions/770.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md) · [CWE-409](https://agentprime.io/advisories/tag/cwe-409.md)
- **Published:** 13 Apr 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 13 Apr 2026, 19:22 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `pillow` (PyPI): affected `>=10.3.0, <12.2.0`; fixed in `12.2.0`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Pillow versions 10.3.0 up to but not including 12.2.0 are affected. When decoding a GZIP-compressed FITS image, Pillow did not limit how much data it read, so a specially crafted FITS file could consume unbounded memory and cause a denial of service through an out-of-memory crash or severe slowdown. Upgrade to Pillow 12.2.0. Alternatively, open only image formats other than FITS by passing an explicit formats list to Image.open.

Written 1 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 8.7 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0067, the 52nd percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:11 UTC: First seen by agentprime
- 31 Oct 2026, 14:11 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-whj4-6x5x-4v2j)

## Sources

- [GitHub Advisory Database: GHSA-whj4-6x5x-4v2j](https://github.com/advisories/GHSA-whj4-6x5x-4v2j)
- [OSV: GHSA-whj4-6x5x-4v2j](https://osv.dev/vulnerability/GHSA-whj4-6x5x-4v2j)
- <https://github.com/python-pillow/Pillow/security/advisories/GHSA-whj4-6x5x-4v2j>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-40192>
- <https://github.com/python-pillow/Pillow/pull/9521>
- <https://github.com/python-pillow/Pillow/commit/3cb854e8b2bab43f40e342e665f9340d861aa628>
- <https://github.com/python-pillow/Pillow>
- <https://pillow.readthedocs.io/en/stable/releasenotes/12.2.0.html#prevent-fits-decompression-bomb>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-whj4-6x5x-4v2j>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-whj4-6x5x-4v2j/>. Everything for agents: <https://agentprime.io/llms.txt>.