CVE-2025-66034

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.

CVSS 3.1

9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

0.5% chance of exploitation in the next 30 days; higher than 45% of CVEs (scores of 2026-10-25)

CWE

CWE-91

Published

2025-11-29

Modified

2026-10-18

Record from

the NVD, synced 2026-10-19

Affected

• fonttools:fonttools

Packages (OSV)

References

• https://github.com/fonttools/fonttools/commit/a696d5ba93270d5954f98e7cab5ddca8a02c1e32
• https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv
• https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv

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