CVE-2025-66034

What it is

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.

At a glance

Exploitability

Can be exploited locally on the machine without logging in, but needs a user to act. High risk of data tampering.

Exploit odds

0.6% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2025-11-29 01:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-18 18:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.6% in the next 30 days (EPSS).
• Severity: 6.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2025-11-29 01:16 UTC

Last modified

2026-10-18 18:10 UTC

Exploit probability

0.6% · EPSS, next 30 days

Weakness

CWE-91

Record status

Analyzed

Affected

• Fonttools < 4.60.2

Attack profile CVSS 3.1 · 6.3

Attack vector

Local

Complexity

High

Privileges needed

None

User interaction

Required

Scope

Changed

Confidentiality

None

Integrity

High

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2025-66034.md and follow it. Check whether this project is affected by CVE-2025-66034. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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