CVE-2025-66034
fontTools is Vulnerable to Arbitrary File Write and XML injection in fontTools.varLib
- Published
- Nov 29, 2025
- Updated
- Dec 1, 2025
- Assigning CNA
- GitHub_M
- Evidence observed
- Aug 8, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HLow · next 30 days
- Percentile
- 44.6%
- Model date
- Oct 15, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
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.
Sources
- CVE-2025-66034Exploit
CVE-2025-66034 - fontTools varLib Arbitrary File Write → RCE PoC exploit for an Arbitrary File Write + XML Injection vulnerability in fontTools.varLib.
- varlib-cve-2025-66034Exploit
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-2025-66034Exploit
CVE-2025-66034 exploit and documentation
- POC-CVE-2025-66034Exploit
Automated exploit for CVE-2025-66034, chaining path traversal and XML injection in fontTools varLib to achieve unauthenticated remote code execution via crafted .designspace file upload.
- CVE-2025-66034-htb-ctfExploit
Exploit for VariaType HTB machine leveraging XML injection in fontTools to achieve RCE via PHP reverse shell payload in .designspace metadata.
- Variatype.htb-CVE-2025-66034Exploit
Python exploit script for CVE-2025-66034 in the HackTheBox Variatype machine, delivering command execution and reverse shell payloads for initial access.
Responsible use
Use vulnerability information only on systems you own or are authorized to test. Kitploit links to public research metadata and does not store exploit code or malicious payloads.