CVE-2025-66034: Fonttools

Critical severity, CVSS 9.8. EPSS: 0.5% chance of exploitation in the next 30 days.

fontTools is a library for manipulating fonts, written in Python. In versions from 4.33.0 to before 4.60.2, the fonttools varLib (or python3 -m fontTools.varLib) script has an arbitrary file write vulnerability that leads to remote code execution when a malicious .designspace file is processed. The vulnerability affects the main() code path of fontTools.varLib, used by the fonttools varLib CLI and any code that invokes fontTools.varLib.main(). This issue has been patched in version 4.60.2.

Affected products

• Fonttools Fonttools: from 4.33.0, before 4.60.2 (fixed in 4.60.2)

Published 2025-11-29. Last modified 2026-06-17.