How to fix CVE-2025-66034?

Within 30 days: Identify affected systems running Python. In and apply vendor patches as part of regular patch cycle. Vendor patch is available.

Is Python affected by CVE-2025-66034?

Organizations using Python. In should be aware of moderate risk from CVE-2025-66034 rated CVSS 6.3. Exploitation could compromise the security of affected deployments. Proof-of-concept code is publicly available. A patch is available and should be applied during regular vulnerability management.

CVE-2025-66034

MEDIUM

2025-11-29 [email protected]

6.3

CVSS 3.1

CVSS Vector

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

Attack Vector

Local

Attack Complexity

High

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

None

Integrity

High

Availability

Low

Lifecycle Timeline

Analysis Generated

Mar 28, 2026 - 19:24 vuln.today

Patch Released

Mar 28, 2026 - 19:24 nvd

Patch available

PoC Detected

Dec 03, 2025 - 21:50 vuln.today

Public exploit code

CVE Published

Nov 29, 2025 - 01:16 nvd

MEDIUM 6.3

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.

Analysis

fontTools is a library for manipulating fonts, written in Python. Rated medium severity (CVSS 6.3), this vulnerability is no authentication required. Public exploit code available.

Technical Context

This vulnerability is classified under CWE-91. 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 include: Fonttools. Version information: before 4.60.2.

Affected Products

Fonttools.

Remediation

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +0.1

CVSS: +32

POC: +20

Vendor Status

CVE-2025-66034 vulnerability details – vuln.today

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CVE-2025-66034

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CVE-2025-66034

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External POC / Exploit Code