Information Disclosure in ag-ui-protocol ag-ui

Executive Summary

CVE-2026-120233 is a security flaw in the ag-ui client library (versions up to 0.0.58) where the HttpAgent component improperly handles HTTP redirects. By default, it follows redirects automatically, which can be exploited by a malicious agent endpoint to redirect the client to an attacker-controlled origin while retaining sensitive authentication headers and request data, leading to information disclosure.

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Detection Guidance

Check if ag-ui-protocol ag-ui versions up to 0.0.58 are installed. Inspect network traffic for unexpected HTTP redirects in POST requests. Monitor for unauthorized data exfiltration or SSRF attempts targeting internal endpoints.

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Impact Analysis

This vulnerability allows an attacker to intercept sensitive data such as run request payloads (including thread IDs, run IDs, and conversation history), non-Authorization headers (like X-Tenant or API keys), and potentially perform client-side request forgery (SSRF) by directing the client to POST to internal endpoints. The attacker gains access to confidential information and can manipulate internal requests.

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Compliance Impact

This vulnerability could lead to breaches of confidentiality and integrity, potentially violating GDPR (data protection) and HIPAA (protected health information) by exposing sensitive user data and credentials. Organizations using affected versions may face compliance violations and legal consequences.

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Mitigation Strategies

Update ag-ui-protocol ag-ui to a patched version. Configure HttpAgent to set redirect: 'error' in requestInit to block automatic redirects. Review and restrict agent endpoints to prevent malicious redirection. Monitor for suspicious POST requests to external or internal origins.

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