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CVE-2026-1721

MediumCVSS 6.2 / 10
Published Feb 13, 2026·Last modified Jul 8, 2026
Affected Components(0)

No affected components available

Description

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.

Risk Scores
Base Score
6.2

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights.

Threat Intelligence
2.2

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.37%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity2026 vulnerabilities
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