How severe is CVE-2025-64501?

CVE-2025-64501 has a CVSS score of 7.6/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2025-64501?

CVE-2025-64501 affects the following packages: prosemirror_to_html (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2025-64501?

Update prosemirror_to_html to 0.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-64501 is resolved across your whole dependency graph.

How do I detect CVE-2025-64501 in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for prosemirror_to_html, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-64501 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2025-64501 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-64501 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-64501?

CVE-2025-64501 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 15th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-64501?

CVE-2025-64501 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2025-64501 published, and has it been updated?

CVE-2025-64501 was published on November 10, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

HIGH severity

CVE-2025-64501 — prosemirror_to_html

HIGHFix: etaminstudio/prosemirror_to_html@4d59f94

CVE-2025-64501 is a high-severity (CVSS 7.6) Cross-site Scripting (XSS) vulnerability in prosemirror_to_html. A fix is available for prosemirror_to_html — see the affected versions and patch details below.

ProsemirrorToHtml: Cross-Site Scripting vulnerability through unescaped HTML attribute values

Also known asGHSA-52c5-vh7f-26fx

Published

Nov 10, 2025

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 27, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-64501.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk+0.02%

Lower risk than most CVEs15th percentile — riskier than 15% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

💎prosemirror_to_html

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Impact

The prosemirror_to_html gem is vulnerable to Cross-Site Scripting (XSS) attacks through malicious HTML attribute values. While tag content is properly escaped, attribute values are not, allowing attackers to inject arbitrary JavaScript code.

Who is impacted:

Any application using prosemirror_to_html to convert ProseMirror documents to HTML
Applications that process user-generated ProseMirror content are at highest risk
End users viewing the rendered HTML output could have malicious JavaScript executed in their browsers

Attack vectors include:

href attributes with javascript: protocol: <a href="javascript:alert(document.cookie)">
Event handlers: <div onclick="maliciousCode()">
onerror attributes on images: <img src=x onerror="alert('XSS')">
Other HTML attributes that can execute JavaScript

Patches

A fix is currently in development. Users should upgrade to version 0.2.1 or later once released.

The patch escapes all HTML attribute values using CGI.escapeHTML to prevent injection attacks.

Workarounds

Until a patched version is available, users can implement one or more of these mitigations:

Sanitize output: Pass the HTML output through a sanitization library like Sanitize or Loofah:

   html = ProsemirrorToHtml.render(document)
   safe_html = Sanitize.fragment(html, Sanitize::Config::RELAXED)

Implement Content Security Policy (CSP): Add strict CSP headers to prevent inline JavaScript execution:

   Content-Security-Policy: default-src 'self'; script-src 'self'

Input validation: If possible, validate and sanitize ProseMirror documents before conversion to prevent malicious content from entering the system.

References

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`prosemirror_to_html`	all versions	0.2.1`bundle update prosemirror_to_html --conservative`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for prosemirror_to_html, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update prosemirror_to_html to 0.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-64501 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Impact The prosemirror_to_html gem is vulnerable to Cross-Site Scripting (XSS) attacks through malicious HTML attribute values. While tag content is properly escaped, attribute values are not, allowing attackers to inject arbitrary JavaScript code. **Who is impacted:** - Any application using prosemirror_to_html to convert ProseMirror documents to HTML - Applications that process user-generated ProseMirror content are at highest risk - End users viewing the rendered HTML output could have malicious JavaScript executed in their browsers **Attack vectors include:** - `href` attributes wit