Critical severity · published Nov 29, 2025
CVE-2025-66034
fontTools is Vulnerable to Arbitrary File Write and XML injection in fontTools.varLib
9.8
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 46% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FO
fonttools · fonttools
>= 4.33.0, < 4.60.2 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66034
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-66034
Patch
https://github.com/fonttools/fonttools/commit/a696d5ba93270d5954f98e7cab5ddca8a02c1e32
Exploit
https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv
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