Arbitrary File Write Vulnerability in fontTools Affects Remote Code Execution
CVE-2025-66034

6.3MEDIUM

Key Information:

Vendor

Fonttools

Status
Fonttools
Vendor
CVE Published:
29 November 2025

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2025-66034?

The fontTools library, used for font manipulation in Python, contains an arbitrary file write vulnerability affecting versions from 4.33.0 to before 4.60.2. This flaw allows an attacker to execute remote code when a specially crafted .designspace file is processed through the fonttools varLib script. The vulnerability resides in the main() method of fontTools.varLib, actionable through the fonttools varLib CLI and any invocation of fontTools.varLib.main(). Users are encouraged to update to version 4.60.2 or later to mitigate this risk.

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Affected Version(s)

fonttools >= 4.33.0, < 4.60.2

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2025-66034-Poc-to-Get-RCE-for-HTB-VariaType
Created by manbahadurthapa1248

varlib-cve-2025-66034
Created by symphony2colour

References

https://github.com/fonttools/fonttools/security/advisorie...
x_refsource_CONFIRM
https://github.com/fonttools/fonttools/commit/a696d5ba932...
x_refsource_MISC

CVSS V3.1

Score:
6.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Local
Attack Complexity:
High
Privileges Required:
None
User Interaction:
Required
Scope:
Changed

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

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