CVE-2025-66034

CRITICALNVD 9.86.3▼
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.3 under NVD CVSS v3. EPSS exploit probability: 0.1%, top 75% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 9.8Exploit: NoneExposed: 0

A fix is available — apply it.

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 v3
9.8
EG Score
6.3(medium)
EPSS
40.2%
KEV
Not listed

Published

November 29, 2025

Last Modified

June 17, 2026

Advisory Details (2)

Auto-updated Jul 5, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github.
github Patch Available🟡 PoC Available

Arbitrary File Write and XML injection in fontTools.varLib · Advisory · fonttools/fonttools · GitHub

https://github.com/fonttools/fonttools/security/advisories/GHSA-768j-98cg-p3fv
github_commit Patch Available

commit a696d5ba9327 (fonttools/fonttools)

Patch available: fonttools/fonttools 4.61.0 (contains commit a696d5ba9327)

https://github.com/fonttools/fonttools/commit/a696d5ba93270d5954f98e7cab5ddca8a02c1e32

Vendor Advisories for CVE-2025-66034(3)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntupython3-fonttools (4.55.3-2ubuntu0.25.10.1) @ questing2026-05-29ubuntu
redhatrhoai/odh-workbench-jupyter-trustyai-cpu-py312-rhel9:17718741812026-03-04redhat
redhatrhoai/odh-openvino-model-server-rhel9:17706214502026-02-12redhat
redhatrhoai/odh-workbench-jupyter-trustyai-cpu-py312-rhel9:17700554252026-02-05redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
fonttools4.33.0 ... 4.60.1 (71 versions)4.60.2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 9× in last 7d / 45× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:24 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:30 UTCEPSS rescore
  5. 2026-07-19 14:30 UTCEPSS rescore
  6. 2026-07-19 02:28 UTCEPSS rescore
  7. 2026-07-18 10:04 UTCEPSS rescore
  8. 2026-07-18 10:04 UTCEPSS rescore
  9. 2026-07-16 17:02 UTCEPSS rescore
  10. 2026-07-15 16:57 UTCEPSS rescore
  11. 2026-07-15 16:57 UTCEPSS rescore
  12. 2026-07-15 01:59 UTCEPSS rescore
  13. 2026-07-15 01:59 UTCEPSS rescore
  14. 2026-07-13 22:29 UTCEPSS rescore
  15. 2026-07-13 06:12 UTCEPSS rescore
  16. 2026-07-12 05:46 UTCEPSS rescore
  17. 2026-07-11 08:27 UTCEPSS rescore
  18. 2026-07-09 19:09 UTCEPSS rescore
  19. 2026-07-08 15:15 UTCEPSS rescore
  20. 2026-07-07 13:46 UTCEPSS rescore
  21. 2026-07-06 16:27 UTCEPSS rescore
  22. 2026-07-06 16:27 UTCEPSS rescore
  23. 2026-07-06 09:11 UTCOSV refresh
  24. 2026-07-06 02:23 UTCEPSS rescore
  25. 2026-07-06 02:23 UTCEPSS rescore
Show 63 more
  1. 2026-07-05 02:30 UTCEPSS rescore
  2. 2026-07-05 02:30 UTCEPSS rescore
  3. 2026-07-04 06:31 UTCEPSS rescore
  4. 2026-07-04 06:30 UTCEPSS rescore
  5. 2026-07-01 15:06 UTCEPSS rescore
  6. 2026-07-01 15:06 UTCEPSS rescore
  7. 2026-06-30 23:22 UTCEPSS rescore
  8. 2026-06-29 14:06 UTCEPSS rescore
  9. 2026-06-29 14:06 UTCEPSS rescore
  10. 2026-06-28 14:07 UTCEPSS rescore
  11. 2026-06-28 14:07 UTCEPSS rescore
  12. 2026-06-28 04:56 UTCEPSS rescore
  13. 2026-06-28 04:55 UTCEPSS rescore
  14. 2026-06-27 03:08 UTCEPSS rescore
  15. 2026-06-25 13:49 UTCEPSS rescore
  16. 2026-06-24 14:04 UTCEPSS rescore
  17. 2026-06-24 14:04 UTCEPSS rescore
  18. 2026-06-24 10:00 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  19. 2026-06-23 21:32 UTCEPSS rescore
  20. 2026-06-23 21:32 UTCEPSS rescore
  21. 2026-06-22 14:25 UTCEPSS rescore
  22. 2026-06-21 14:56 UTCEPSS rescore
  23. 2026-06-21 14:56 UTCEPSS rescore
  24. 2026-06-21 01:59 UTCEPSS rescore
  25. 2026-06-21 01:59 UTCEPSS rescore
  26. 2026-06-19 19:25 UTCEPSS rescore
  27. 2026-06-19 19:25 UTCEPSS rescore
  28. 2026-06-18 17:52 UTCEPSS rescore
  29. 2026-06-18 17:52 UTCEPSS rescore
  30. 2026-06-17 21:05 UTCOSV refresh
  31. 2026-06-17 17:52 UTCEPSS rescore
  32. 2026-06-16 17:52 UTCEPSS rescore
  33. 2026-06-15 17:48 UTCEPSS rescore
  34. 2026-06-15 17:48 UTCEPSS rescore
  35. 2026-06-14 23:18 UTCEPSS rescore
  36. 2026-06-13 23:00 UTCEPSS rescore
  37. 2026-06-13 23:00 UTCEPSS rescore
  38. 2026-06-12 23:11 UTCEPSS rescore
  39. 2026-06-11 14:00 UTCEPSS rescore
  40. 2026-06-10 22:18 UTCEPSS rescore
  41. 2026-06-10 22:18 UTCEPSS rescore
  42. 2026-06-10 13:22 UTCEPSS rescore
  43. 2026-06-08 14:17 UTCEPSS rescore
  44. 2026-06-08 14:16 UTCEPSS rescore
  45. 2026-06-07 15:24 UTCEPSS rescore
  46. 2026-06-07 15:24 UTCEPSS rescore
  47. 2026-06-06 13:47 UTCEPSS rescore
  48. 2026-06-06 13:47 UTCEPSS rescore
  49. 2026-06-05 22:46 UTCEPSS rescore
  50. 2026-06-05 22:46 UTCEPSS rescore
  51. 2026-06-05 06:10 UTCEPSS rescore
  52. 2026-06-05 06:10 UTCEPSS rescore
  53. 2026-06-04 13:12 UTCEPSS rescore
  54. 2026-06-04 13:12 UTCEPSS rescore
  55. 2026-06-02 20:13 UTCEPSS rescore
  56. 2026-06-02 20:12 UTCEPSS rescore
  57. 2026-06-01 13:51 UTCEPSS rescore
  58. 2026-06-01 13:51 UTCEPSS rescore
  59. 2026-05-31 00:16 UTCEPSS rescore
  60. 2026-05-31 00:16 UTCEPSS rescore
  61. 2026-05-29 18:45 UTCEG score recompute
  62. 2026-05-29 18:45 UTCVendor advisory
  63. 2026-05-29 13:44 UTCEPSS rescore

Publicly available exploits

(3 references)

Working exploit code is in the public domain (3 GitHub PoCs). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCv3cn4x00/POC-CVE-2025-66034
    First seen Mar 21, 2026
    Open source ↗
  • GitHub PoCLiquid1998/Variatype.htb-CVE-2025-66034
    First seen Mar 16, 2026
    Open source ↗
  • GitHub PoCsymphony2colour/varlib-cve-2025-66034
    First seen Mar 15, 2026

    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.

    Open source ↗

Frequently asked(5)

What is CVE-2025-66034?
CVE-2025-66034 is a critical vulnerability published on November 29, 2025. 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…
When was CVE-2025-66034 disclosed?
CVE-2025-66034 was first published in the National Vulnerability Database on November 29, 2025, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-66034 actively exploited?
CVE-2025-66034 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 40.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2025-66034?
CVE-2025-66034 has a CVSS v3 base score of 9.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 6.3.
How do I remediate CVE-2025-66034?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-66034, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2025-66034

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