What is the CVSS score of CVE-2023-45139?

CVE-2023-45139 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. EPSS exploitation probability: 0.2%.

Is there a public PoC exploit available for CVE-2023-45139?

Yes, a public proof-of-concept exploit is available for CVE-2023-45139. Prioritise patching immediately. EPSS: 0.2%.

How to fix or mitigate CVE-2023-45139?

Within 30 days: Identify all affected systems and apply vendor patches as part of regular patch cycle. Vendor patch is available.

Fonttools CVE-2023-45139

HIGH

Improper Restriction of XML External Entity Reference (CWE-611)

2024-01-10 security-advisories@github.com

Python XXE Fonttools

7.5

CVSS 3.1 · GitHub Advisory

View

Vulnerability Assessment

Weakness	CWE CWE-611 OWASP Top 10:2025 A02:2025 - Security Misconfiguration ASVS 5.0 V13 - Configuration XML external entity prevention MITRE ATT&CK 2 techniques across 2 tactics: Initial Access, Collection The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available. EPSS exploitation probability: 0.17%.
Exploit ScenarioDerived	A remote attacker could read arbitrary files or perform SSRF through XML processing by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 28, 2026

fontTools is a library for manipulating fonts, written in Python. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

Earlier versions of this analysis (1)

v1 Mar 28, 2026 - 19:34 CVSS 7.5

XXE in fontTools.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Disable external entity processing in XML parsers, use JSON instead of XML where possible.

Affected Packages

pypi fonttools fix: 4.43.0

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in pypi

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as XML External Entity (XXE) (CWE-611), which allows attackers to read arbitrary files or perform SSRF through XML processing. fontTools is a library for manipulating fonts, written in Python. The subsetting module has a XML External Entity Injection (XXE) vulnerability which allows an attacker to resolve arbitrary entities when a candidate font (OT-SVG fonts), which contains a SVG table, is parsed. This allows attackers to include arbitrary files from the filesystem fontTools is running on or make web requests from the host system. This vulnerability has been patched in version 4.43.0. Affected products include: Fonttools. Version information: version 4.43.0..

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

GitHub Advisory PRIMARY 7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Lifecycle Timeline

Patch released

Mar 28, 2026 - 19:34 nvd

Patch available

PoC Detected

Nov 21, 2024 - 08:26 vuln.today

Public exploit code

CVE Published

Jan 10, 2024 - 16:15 nvd

HIGH 7.5

DescriptionGitHub Advisory

fontTools is a library for manipulating fonts, written in Python. The subsetting module has a XML External Entity Injection (XXE) vulnerability which allows an attacker to resolve arbitrary entities when a candidate font (OT-SVG fonts), which contains a SVG table, is parsed. This allows attackers to include arbitrary files from the filesystem fontTools is running on or make web requests from the host system. This vulnerability has been patched in version 4.43.0.

Executive ViewAI

Why It Matters

Organizations using fontTools face notable risk from CVE-2023-45139, a XML external entity vulnerability rated CVSS 7.5. Exploitation could compromise the security of affected deployments. Proof-of-concept code is publicly available, increasing the risk of exploitation. A patch is available and should be applied as part of regular vulnerability management.

Business Impact: High

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.

Threat Intelligence Overview

EPSS Score

0.2%

Top 62% exploitable

Exploit

POC

Public exploit code exists

Data Quality

4 sources

Confidence: Medium

NVD

CVE.org

EPSS

GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC Yes

EPSS 0.2%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.