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Fencer Intel
medium 6.3

CVE-2025-66034 json

fontTools is Vulnerable to Arbitrary File Write and XML injection in fontTools.varLib

published 11mo ago modified 22d ago also EUVD-2025-199882 , GHSA-768j-98cg-p3fv , PYSEC-2026-1389

cvss
6.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits
0
none known

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.

Patch / fix

  • pypi fonttools 4.60.2
  • fonttools fonttools 4.60.2
  • fonttools Debian 12 4.38.0-1+deb12u1
  • fonttools Debian 13 4.57.0-1+deb13u1
  • fonttools Debian 14 4.61.1-1

debian advisories DEBIAN-CVE-2025-66034

  • fonttools Ubuntu 25.10 4.55.3-2ubuntu0.25.10.1
  • fonttools Ubuntu 26.04 LTS 4.57.0-3ubuntu1
  • fonttools Ubuntu Pro 24.04 LTS 4.46.0-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2025-66034

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-FontTools SLES for SAP applications 16.0, SLES 16.0 4.53.1-160000.3.1
  • python-FontTools SLE Module for Package Hub 15 SP7, openSUSE Leap 15.6 4.47.2-150600.3.3.1

suse advisories SUSE-SU-2026:20184-1SUSE-SU-2026:0199-1

  • python-FontTools openSUSE Leap 16.0 4.53.1-160000.3.1
  • python-FontTools openSUSE Tumbleweed 4.61.1-1.1

opensuse advisories openSUSE-SU-2026:20119-1openSUSE-SU-2026:10076-1

Is CVE-2025-66034 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-66034 updated cvss 6.3

fonttools: fontTools: Arbitrary file write leading to remote code execution via malicious .designspace file

  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-tech-preview/automation-dashboard-rhel9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 7 fonttools Red Hat Enterprise Linux AI (RHEL AI) rhelai1/bootc-amd-rhel9, rhelai1/bootc-intel-rhel9, rhelai1/bootc-nvidia-rhel9, rhelai1/bootc-azure-amd-rhel9, rhelai1/instructlab-amd-rhel9, rhelai1/bootc-aws-nvidia-rhel9, +4 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat OpenShift AI 2.25 rhoai 1770053703, rhoai 1770053721, rhoai 1770053723, rhoai 1770053730, rhoai 1770053740, rhoai 1770053748, +13 more
    fixed: vendor fix RHSA-2026:2106
  • Red Hat OpenShift AI 3.3 rhoai 1769162595, rhoai 1770754585, rhoai 1770754605, rhoai 1770754646, rhoai 1771415661, rhoai 1771502843, +14 more
    fixed: vendor fix RHSA-2026:3713
  • Red Hat OpenShift AI 2.25 rhoai 1770053626, rhoai 1770053627, rhoai 1770053694, rhoai 1770053728, rhoai 1770053733, rhoai 1770053784, +82 more Red Hat OpenShift AI 3.3 rhoai 1769436305, rhoai 1769519975, rhoai 1770277795, rhoai 1770735854, rhoai 1770788873, rhoai 1770956034, +53 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
11mo ago

Exploit prediction

0.59% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.3 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:L
GitHub 3.1 6.3 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:L
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
OSV 3.1 6.3 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:L

Affected packages

ecosystem package affected fixed in
pypi fonttools
>=4.33.0, <4.60.2
4.60.2

Affected products

  • fonttools fonttools

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.