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Full vulnerability report · 2025
CVE-2025-66034High confidence

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

fonttools · fonttools

Official source article: GitHub GHSA-768J-98CG-P3FV ↗. Check the applicable product and release in the original source.

6.3MediumCVSS 3.1
Recommended action
Within 7 days

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • EPSS is 0.55% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs fonttools fonttools and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

5 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourcefonttoolsVendor fix publishedDebian records a fixed source-package version for this release.4.57.0-1+deb13u1Debian Security Tracker ↗Source updated 6 Oct 2026
Debian bookwormbookworm · sourcefonttoolsVendor fix publishedDebian records a fixed source-package version for this release.4.38.0-1+deb12u1Debian Security Tracker ↗Source updated 6 Oct 2026
Debian forkyforky · sourcefonttoolsVendor fix publishedDebian records a fixed source-package version for this release.4.61.1-1Debian Security Tracker ↗Source updated 6 Oct 2026
Debian sidsid · sourcefonttoolsVendor fix publishedDebian records a fixed source-package version for this release.4.61.1-1Debian Security Tracker ↗Source updated 6 Oct 2026
Ubuntu 24.04 LTSnoble · esm-appsfonttoolsVendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.4.46.0-1ubuntu0.1~esm1Canonical Ubuntu Security ↗Source updated 5 Oct 2026
Open-source package ranges2 source-attributed ranges

These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.

Ecosystem and packageAffected rangeFirst fixed versionEvidence
PyPIfonttoolsECOSYSTEM: introduced 4.33.0; fixed 4.60.24.60.2OSV record ↗aggregator derived · 10 Sep 2026
pipfonttools>= 4.33.0, < 4.60.24.60.2GitHub advisory ↗upstream repository advisory · 1 Dec 2025
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2025-66034 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityfonttools: fontTools: Arbitrary file write leading to remote code execution via malicious .designspace file
12 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • ansible-automation-platform-tech-preview/automation-dashboard-rhel9 as a component of Red Hat Ansible Automation Platform 2
  • fonttools.src as a component of Red Hat Enterprise Linux 7
  • rhelai1/bootc-amd-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
  • rhelai1/bootc-aws-nvidia-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
  • rhelai1/bootc-azure-amd-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
  • rhelai1/bootc-azure-nvidia-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
  • rhelai1/bootc-gcp-nvidia-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
  • rhelai1/bootc-intel-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
  • rhelai1/bootc-nvidia-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
  • rhelai1/instructlab-amd-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
  • rhelai1/instructlab-intel-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
  • rhelai1/instructlab-nvidia-rhel9 as a component of Red Hat Enterprise Linux AI (RHEL AI)
Summary
This vulnerability in fontTools varLib allows a crafted .designspace file to trigger arbitrary file writes and XML-based content injection during variable-font generation. Because filenames are not sanitized, an attacker can use path traversal to overwrite files anywhere on the filesystem, and malicious payloads embedded in XML labelname elements can be injected directly into the generated output. When these overwritten files reside in executable or web-served locations, this can enable local remote-code execution or corruption of application or configuration files. The issue affects the varLib CLI and any code that invokes fontTools.varLib.main().
Remediation
For Red Hat OpenShift AI 2.25.2 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update: https://docs.redhat.com/en/documentation/red_hat_openshift_ai/
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2025-199882

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

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.

What

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.

Why

The product does not properly neutralize special elements that are used in XML, allowing attackers to modify the syntax, content, or commands of the XML before it is processed by an end system.

How

An attacker operating through local access may attempt exploitation without authentication after a user interaction. If successful, the issue may execute code or commands in the affected security context.

What

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.

Why

The product does not properly neutralize special elements that are used in XML, allowing attackers to modify the syntax, content, or commands of the XML before it is processed by an end system.

How

An attacker operating through local access may attempt exploitation without authentication after a user interaction. If successful, the issue may execute code or commands in the affected security context.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
local access → XML Injection (aka Blind XPath Injection) → execute code or commands in the affected security context
Attack surface
Local
Privileges required
None: unauthenticated exploitation is possible
User interaction
Required interaction required
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Changed: exploitation can affect a different security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-91 ↗

CWE-91: XML Injection (aka Blind XPath Injection). The product does not properly neutralize special elements that are used in XML, allowing attackers to modify the syntax, content, or commands of the XML before it is processed by an end system.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:L

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SChangedScope: The attack can affect a component governed by a different security authority.CNoneConfidentiality impact: No direct loss is represented by this metric.IHighIntegrity impact: A successful attack can cause a major loss.ALowAvailability impact: A successful attack can cause a limited loss.
Post-exploitation / living off the land
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
UnauthenticatedRemote code executionCWE-91Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-2189Dell PowerProtect Data Domain: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Dell PowerProtect Data Domain ausnutzen, um seine Privilegien zu erhöhen um beliebigen Programmcode auszuführen, um Sicherheitsvorkehrungen zu umgehen, um einen Denial of Service Angriff durchzuführen, um einen Cross-Site Scripting Angriff durchzuführen, um Informationen offenzulegen, und um Dateien zu manipulieren.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20251203Security Bulletin 03 Dec 2025

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 03 Dec 2025, published on 3 December 2025. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0556Multiples vulnérabilités dans les produits VMware

rd?id=CVE-2025-6075 Référence CVE CVE-2025-61726 https://www.cve.org/CVERecord?id=CVE-2025-61726 Référence CVE CVE-2025-61727 https://www.cve.org/CVERecord?id=CVE-2025-61727 Référence CVE CVE-2025-61728 https://www.cve.org/CVERecord?id=CVE-2025-61728 Référence CVE CVE-2025-61729 https://www.cve.org/CVERecord?id=CVE-2025-61729 Référence CVE CVE-2025-61730 https://www.cve.org/CVERecord?id=CVE-2025-61730 Référence CVE CVE-2025-61731 https://www.cve.org/CVERecord?id=CVE-2025-61731 Référence CVE CVE-2025-61732 https://www.cve.org/CVERecord?id=CVE-2025-61732 Référence CVE CVE-2025-62813 https://www.cve.org/CVERecord?id=CVE-2025-62813 Référence CVE CVE-2025-66034 https://www.cve.org/CVERecord?id=CVE-2025-66034 Référence CVE CVE-2025-66221 https://www.cve.org/CVERecord?id=CVE-2025-66221 Référence CVE CVE-2025-6638 https://www.cve.org/CVERecord?id=CVE-2025-6638 Référence CVE CVE-2025-66418 https://www.cve.org/CVERecord?id=CVE-2025-66418 Référence CVE CVE-2025-66471 https://www.cve.org/CVERecord?id=CVE-2025-66471 Référence CVE CVE-2025-66516 https://www.cve.org/CVERecord?id=CVE-2025-66516 Référence CVE CVE-2025-66614 https://www.cve.org/CVERecord?id=CVE-2025-66614 Référence CVE CVE-2025-67221 https://www.cve.org/CVERecord?id=CVE-2025-67221 Référence CVE CVE-2025-68121 https://www.cve.org/CVERecord?id=CV

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2025-021086Python 用 fonttools におけるブラインド XPath インジェクションの脆弱性

Python 用 fonttools には、ブラインド XPath インジェクションの脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
Action
For Red Hat OpenShift AI 2.25.2 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update: https://docs.redhat.com/en/documentation/red_hat_openshift_ai/
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 29 Nov 2025 · Last source change 1 Dec 2025, 14:11 UTC · CWE-91 · XML Injection (aka Blind XPath Injection)

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2025-199882
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    >= 4.33.0, < 4.60.2 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    >= 4.33.0, < 4.60.2 · Fixed: For Red Hat OpenShift AI 2.25.2 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this errata update: https://docs.redhat.com/en/documentation/red_hat_openshift_ai/
    Red Hat Product Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2025-199882↗Red Hat Product Security security advisory↗CISA Vulnrichment SSVC evidence↗Public exploit reference · GitHub GHSA-768J-98CG-P3FV↗Patch or update reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2025-66034 · cve.blacktree.nl