How severe is CVE-2025-66034?

CVE-2025-66034 has a CVSS 3.x base score of 6.3, rated medium severity. It is exploitable over local access with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability low.

Is CVE-2025-66034 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-66034?

CVE-2025-66034 affects Fonttools. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-66034?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-66034 have an EU (EUVD) identifier?

Yes. CVE-2025-66034 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-199882.

When was CVE-2025-66034 published?

CVE-2025-66034 was published on 2025-11-29 and last updated on 2026-06-17.

CVE-2025-66034

CVE-2025-66034 is a medium-severity vulnerability in Fonttools with a CVSS 3.x base score of 6.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-91.

Key facts

Severity: Medium (CVSS 3.x base score 6.3)
EPSS exploit prediction: 0% (39th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-199882
Weakness: CWE-91
Affected product: Fonttools
Published: 2025-11-29
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2025-66034?: 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.
How severe is CVE-2025-66034?: CVE-2025-66034 has a CVSS 3.x base score of 6.3, rated medium severity. It is exploitable over local access with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability low.
Is CVE-2025-66034 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-66034?: CVE-2025-66034 affects Fonttools. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-66034?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-66034 have an EU (EUVD) identifier?: Yes. CVE-2025-66034 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-199882.
When was CVE-2025-66034 published?: CVE-2025-66034 was published on 2025-11-29 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:fonttools:fonttools:*:*:*:*:*:python:*:*

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