Pillow: Invalid free in FreeType glyph rendering with active stroker

Summary

Pillow, a Python imaging library, contains an invalid free of a FreeType glyph pointer when text is drawn with a non-zero stroke width. An attacker who can supply a malformed font file as untrusted bytes to an application that renders text with stroke can trigger the glyph-load error path. Successful exploitation can corrupt memory or crash the process, resulting in a Denial of Service.

Affected

• Pillow 10.0.0 up to and including 12.3.0
• Pillow is often a transitive dependency, so check indirect installations and container images

Fixed in

• Pillow 13.0.0 (upstream fix, commit a7416de7f3a43128179d2cf68df3240ea8dafe13)
• Pillow 13.0.0 requires Python 3.11 or newer
• Unknown: whether a backport to earlier versions will be released; the release notes say backports should not be expected

Workaround

• No vendor-documented workaround.
• Analyst suggestion: do not render untrusted font files with a non-zero stroke width until patched.
• Analyst suggestion: restrict font uploads or run font rendering in an isolated worker process.

Exploitation

• Not listed in CISA KEV.
• No known in-the-wild exploitation reported.
• The GHSA advisory is public and describes the trigger path; a public PoC is referenced in the advisory.
• CISA SSVC: exploitation status poc, automatable yes, technical impact partial.

Our recommendation

• Inventory Python environments, container images and wheels for Pillow 10.0.0 to 12.3.0, including transitive dependencies.
• Upgrade to Pillow 13.0.0 or later and plan for Python 3.11 or newer.
• Prioritize systems that render user-supplied fonts with stroke, such as document generators or image services.
• Rebuild container images that bundle an older copy.

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

• GitHub Security Advisory GHSA-j4m9-6w36-pw47 github.com
• Pillow fix commit a7416de7f3a43128179d2cf68df3240ea8dafe13 github.com
• Pillow release 13.0.0 github.com
• OpenCVE CVE-2026-112893 app.opencve.io
• Rapid7 CVE-2026-112893 www.rapid7.com

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 15:38.