CVE-2025-50055 Overview
CVE-2025-50055 is a Cross-Site Scripting (XSS) vulnerability in the Security Assertion Markup Language (SAML) Authentication module of OpenVPN Access Server. Affected versions include 2.14.0 through 2.14.3. The flaw allows configured remote SAML Assertion Consumer Service (ACS) endpoint servers to inject arbitrary web script or HTML through the RelayState parameter. The vulnerability is categorized under [CWE-79] Improper Neutralization of Input During Web Page Generation.
Critical Impact
A configured SAML ACS endpoint can inject arbitrary scripts into the OpenVPN Access Server web context via RelayState, potentially compromising administrator or user sessions.
Affected Products
- OpenVPN Access Server 2.14.0
- OpenVPN Access Server 2.14.1 through 2.14.2
- OpenVPN Access Server 2.14.3
Discovery Timeline
- 2025-10-27 - CVE-2025-50055 published to the National Vulnerability Database (NVD)
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-50055
Vulnerability Analysis
The SAML Authentication module in OpenVPN Access Server processes the RelayState parameter returned from a SAML Assertion Consumer Service (ACS) endpoint. The application fails to properly neutralize script content contained within this parameter before rendering it in the browser context.
An attacker controlling or influencing a configured remote ACS endpoint can craft a RelayState value containing JavaScript or HTML payloads. When the Access Server processes the SAML response and reflects RelayState into a page, the injected script executes in the victim's browser under the Access Server origin.
Because the attack requires interaction with a configured SAML integration, exploitation depends on control over an authorized ACS endpoint or the ability to manipulate SAML responses returned to the Access Server. Successful exploitation can expose session tokens, administrative interface elements, and configuration data accessible from the browser.
Root Cause
The root cause is missing or insufficient output encoding of the RelayState parameter within the SAML authentication flow. User-controllable data flows from an external SAML transaction into HTML rendering without contextual sanitization, satisfying the classic [CWE-79] pattern.
Attack Vector
Exploitation occurs over the network through the SAML authentication flow. An attacker with control of a configured ACS endpoint returns a SAML response with a malicious RelayState value. When a user or administrator completes SAML authentication, the payload executes in their browser session tied to the Access Server web interface.
See the OpenVPN Access Server 3.0 Release Notes for remediation context and technical details.
Detection Methods for CVE-2025-50055
Indicators of Compromise
- SAML authentication responses containing RelayState values with <script>, javascript:, onerror=, or encoded HTML payloads.
- Unexpected outbound requests from administrator browsers immediately after SAML login events.
- Access Server web sessions originating from unusual geolocations following SAML authentication.
- Audit logs showing SAML logins associated with modified administrative configurations.
Detection Strategies
- Inspect web server and reverse proxy logs for RelayState query parameters containing HTML tags, event handlers, or encoded script markers.
- Correlate SAML authentication events with subsequent administrative actions to identify session takeover attempts.
- Deploy a Content Security Policy (CSP) reporting endpoint to capture inline script violations originating from the Access Server web UI.
Monitoring Recommendations
- Enable verbose logging for the SAML Authentication module and forward events to a centralized SIEM for parameter inspection.
- Alert on any RelayState value exceeding expected length or containing non-alphanumeric characters beyond standard URL encoding.
- Monitor identity provider configurations for unauthorized additions or modifications of ACS endpoint URLs.
How to Mitigate CVE-2025-50055
Immediate Actions Required
- Upgrade OpenVPN Access Server to version 3.0.0 or later, which addresses the SAML RelayState handling issue.
- Audit all configured SAML ACS endpoints and remove any that are not explicitly trusted and required.
- Rotate session tokens and administrator credentials if SAML integrations were exposed to untrusted parties.
Patch Information
OpenVPN Access Server 3.0.0 remediates the vulnerability. Review the OpenVPN Access Server 3.0 Release Notes for upgrade procedures and compatibility notes before deployment.
Workarounds
- Restrict SAML ACS endpoint configurations to trusted, internally managed identity providers only.
- Enforce a strict Content Security Policy on the Access Server web interface to block inline script execution.
- Require administrators to authenticate to the Access Server web UI through a separate, non-SAML path where feasible until patches are applied.
# Verify installed OpenVPN Access Server version and plan upgrade to 3.0.0+
sacli Version
apt-get update && apt-get install --only-upgrade openvpn-as
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
