CVE-2025-66034: fonttools — Exploit & Fix

Description

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.

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CVSS v3.1 Score

6.3

MEDIUM

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

Weakness Type (CWE)

CWE-91 CWE-91

Affected Products

Vendor	Product	Versions
fonttools	fonttools	4.33.0 — 4.60.2

References

Advisories & Patches

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

Exploits

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

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 6.3 (MEDIUM).

How severe is CVE-2025-66034? +

CVE-2025-66034 has a CVSS v3.1 score of 6.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-66034? +

CVE-2025-66034 affects products from fonttools, specifically: fonttools. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-66034? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2025-66034

Description

CVSS v3.1 Score

Weakness Type (CWE)

Affected Products

References

Advisories & Patches

Exploits

Frequently Asked Questions

Related Vulnerabilities

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