GHSA-CVHV-6XM6-C3V4

Vulnerability from github – Published: 2026-02-13 03:31 – Updated: 2026-02-13 20:04
VLAI?
Summary
Cloudflare Agents is Vulnerable to Reflected Cross-Site Scripting in the AI Playground's OAuth callback handler
Details

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 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.
Severity ?
6.2 (Medium)
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
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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "agents"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.3.10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-1721"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-13T20:04:55Z",
    "nvd_published_at": "2026-02-13T03:15:52Z",
    "severity": "MODERATE"
  },
  "details": "Summary\n\nA Reflected Cross-Site Scripting (XSS) vulnerability was discovered in the AI Playground\u0027s 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\u0027s session.\n\nRoot cause\n\nThe 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 `\u003cscript\u003e` tag.\n\nImpact\n\nAn attacker could craft a malicious link that, when clicked by a victim, would:\n\n  *  Steal user chat message history - Access all LLM interactions stored in the user\u0027s session.\n\n\n  *  Access connected MCP Servers - Interact with any MCP servers connected to the victim\u0027s session (public or authenticated/private), potentially allowing the attacker to perform actions on the victim\u0027s behalf\n\n\nMitigation:\n\n  *  PR:\u00a0 https://github.com/cloudflare/agents/pull/841 https://github.com/cloudflare/agents/pull/841 \n  *  Agents-sdk users should upgrade to\u00a0agents@0.3.10\n  *  Developers using configureOAuthCallback with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.",
  "id": "GHSA-cvhv-6xm6-c3v4",
  "modified": "2026-02-13T20:04:56Z",
  "published": "2026-02-13T03:31:23Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-1721"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cloudflare/agents/pull/841"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cloudflare/agents/commit/3f490d045844e4884db741afbb66ca1fe65d4093"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/cloudflare/agents"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Cloudflare Agents is Vulnerable to Reflected Cross-Site Scripting in the AI Playground\u0027s OAuth callback handler"
}


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