Skip to content
Fencer Intel
medium 6.2

GHSA-w5cr-2qhr-jqc5 json

Cloudflare Agents has a Reflected Cross-Site Scripting (XSS) vulnerability in AI Playground site

published 9mo ago modified 9mo ago

cvss
6.2
version 4.0, the maintainers
cisa kev
Not listed
not in CISA's catalog
epss
—
no score, EPSS covers CVEs only
public exploits
0
none known

Summary

## Summary

A Reflected Cross-Site Scripting (XSS) vulnerability was discovered in the AI Playground's OAuth callback handler. The error_description query parameter was directly interpolated into an HTML script tag without proper escaping, allowing attackers to execute arbitrary JavaScript in the context of the victim's session.

### Root cause

The OAuth callback handler in `site/ai-playground/src/server.ts` directly interpolated the `authError` value, sourced from the `error_description` query parameter, into an inline `<script>` tag.

### Impact

An attacker could craft a malicious link that, when clicked by a victim, would: - Steal user chat message history - Access all LLM interactions stored in the user's session. - Access connected MCP Servers - Interact with any MCP servers connected to the victim's session (public or authenticated/private), potentially allowing the attacker to perform actions on the victim's behalf

### Mitigation:

- PR: https://github.com/cloudflare/agents/pull/841 - Agents-sdk users should upgrade to `agents@0.3.10` - Developers using `configureOAuthCallback` with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.

### Credits

Disclosed responsibly by Nishant Kumawat

Patch / fix

  • npm agents 0.3.10

Is GHSA-w5cr-2qhr-jqc5 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

CVSS scores

assigned by version score vector
the maintainers 4.0 6.2 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N

Affected packages

ecosystem package affected fixed in
npm agents
<0.3.10
0.3.10

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of cloudflare/agents published their own advisory on GitHub. Reviewed sources take precedence over it.