# Pillow \`PcfFontFile.\_load_bitmaps()\`: \`Image.frombytes()\` called without \`\_decompression_bomb_check()\` — bomb protection bypass via PCF font loading

Advisory record · `GHSA-8v84-f9pq-wr9x`

- **Identifiers:** `GHSA-8v84-f9pq-wr9x` · `BIT-pillow-2026-54059` · `CVE-2026-54059` · `PYSEC-2026-2253`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-789](https://cwe.mitre.org/data/definitions/789.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 20 Jul 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 20 Jul 2026, 21:08 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `pillow` (PyPI): affected `<12.3.0`; fixed in `12.3.0`

## Machine-written summary

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

> Pillow versions before 12.3.0 are affected: when loading PCF font files, PcfFontFile.\_load_bitmaps() skips Pillow's decompression bomb check, so glyph images can be allocated far beyond the normal size limit. An attacker who can get an application to load a crafted PCF font from an untrusted source can cause large memory allocations, leading to denial of service. Upgrade to Pillow 12.3.0 or later, which contains the fix; the source does not list a workaround.

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

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0041, the 35th percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 3 Jul 2026, 08:33 UTC: [Published by the maintainers as a GitHub repository advisory](https://github.com/python-pillow/Pillow/security/advisories/GHSA-8v84-f9pq-wr9x)
- 31 Oct 2026, 14:11 UTC: First seen by agentprime
- 31 Oct 2026, 14:11 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-8v84-f9pq-wr9x)

## Sources

- [GitHub Advisory Database: GHSA-8v84-f9pq-wr9x](https://github.com/advisories/GHSA-8v84-f9pq-wr9x)
- [OSV: GHSA-8v84-f9pq-wr9x](https://osv.dev/vulnerability/GHSA-8v84-f9pq-wr9x)
- <https://github.com/python-pillow/Pillow/security/advisories/GHSA-8v84-f9pq-wr9x>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-54059>
- <https://github.com/python-pillow/Pillow/commit/0a263e6264aa5399988d9acd3bbfbca2ca3ec77d>
- <https://github.com/pypa/advisory-database/tree/main/vulns/pillow/PYSEC-2026-2253.yaml>
- <https://github.com/python-pillow/Pillow>
- <https://github.com/python-pillow/Pillow/blob/main/docs/releasenotes/12.3.0.rst>

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-8v84-f9pq-wr9x>, 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-8v84-f9pq-wr9x/>. Everything for agents: <https://agentprime.io/llms.txt>.