CVE-2025-66034
fontTools is Vulnerable to Arbitrary File Write and XML injection in fontTools.varLib
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.
INFO
Published Date :
Nov. 29, 2025, 1:16 a.m.
Last Modified :
Dec. 3, 2025, 9:50 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | CRITICAL | [email protected] |
Solution
- Update fontTools to version 4.60.2.
- Avoid processing malicious .designspace files.
- Verify integrity of input files.
Public PoC/Exploit Available at Github
CVE-2025-66034 has a 8 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-66034.
| URL | Resource |
|---|---|
| https://github.com/fonttools/fonttools/commit/a696d5ba93270d5954f98e7cab5ddca8a02c1e32 | Patch |
| https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv | Exploit Vendor Advisory |
| https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv | Exploit Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-66034 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-66034
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
CVE-2025-66034 - fontTools varLib Arbitrary File Write → RCE PoC exploit for an Arbitrary File Write + XML Injection vulnerability in fontTools.varLib.
Python
None
Python
HACKTHEBOX
Python
CVE-2025-66034 exploit and documentation
Python
None
None
Python
None
Python
Proof-of-concept exploit for CVE-2025-66034 in the fontTools variable font generation pipeline. A crafted .designspace file allows control of the output path, enabling arbitrary file writes. The script automates payload creation, font generation, and upload to demonstrate the issue.
cve-2025-66034
Python
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-66034 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2025-66034 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Dec. 03, 2025
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:fonttools:fonttools:*:*:*:*:*:python:*:* versions from (including) 4.33.0 up to (excluding) 4.60.2 Added Reference Type GitHub, Inc.: https://github.com/fonttools/fonttools/commit/a696d5ba93270d5954f98e7cab5ddca8a02c1e32 Types: Patch Added Reference Type CISA-ADP: https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv Types: Exploit, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Dec. 01, 2025
Action Type Old Value New Value Added Reference https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv -
New CVE Received by [email protected]
Nov. 29, 2025
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:L/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:L Added CWE CWE-91 Added Reference https://github.com/fonttools/fonttools/commit/a696d5ba93270d5954f98e7cab5ddca8a02c1e32 Added Reference https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv