CVE-2025-41064: OpenSIAC Auth Bypass Vulnerability

CVE-2025-41064 Overview

CVE-2025-41064 is an incorrect authentication vulnerability affecting OpenSIAC, a platform developed by GTTS Group. This critical flaw allows attackers to bypass authentication controls and impersonate legitimate users who utilize Cl@ve as their authentication method. Cl@ve is a Spanish government identity verification system used for secure access to public administration services, making this vulnerability particularly concerning for government-related applications.

Critical Impact

Attackers can impersonate any user authenticating via Cl@ve, potentially gaining unauthorized access to sensitive government services and personal data.

Affected Products

• OpenSIAC (GTTS Group) - versions utilizing Cl@ve authentication integration
• Systems implementing OpenSIAC with Cl@ve authentication method enabled

Discovery Timeline

• 2025-10-02 - CVE-2025-41064 published to NVD
• 2025-10-02 - Last updated in NVD database

Technical Details for CVE-2025-41064

Vulnerability Analysis

This vulnerability falls under CWE-287 (Improper Authentication), indicating a fundamental flaw in how OpenSIAC validates user identity during the Cl@ve authentication process. The vulnerability enables authentication bypass, allowing an attacker to successfully authenticate as another user without possessing valid credentials.

The authentication mechanism fails to properly verify the identity assertions received during the Cl@ve authentication flow. This could stem from insufficient validation of authentication tokens, improper handling of identity attributes, or flawed verification of the authentication response from the Cl@ve identity provider.

Root Cause

The root cause is improper authentication handling within OpenSIAC's Cl@ve integration. The system does not adequately verify that the identity claims presented during authentication are legitimate and correspond to the actual authenticated user. This allows attackers to manipulate authentication parameters or forge identity assertions to assume another user's identity.

Attack Vector

The attack is network-based and requires no authentication or user interaction to exploit. An attacker can target the authentication endpoint remotely, making this vulnerability particularly dangerous for internet-facing deployments of OpenSIAC.

The exploitation typically involves intercepting or manipulating the authentication flow between the user, OpenSIAC, and the Cl@ve identity provider. By crafting malicious authentication requests or modifying identity assertion responses, an attacker can convince OpenSIAC that they are a different, legitimate user.

The attack does not require valid credentials or prior access to the system. The attacker simply needs network access to the OpenSIAC authentication endpoint and knowledge of the target user's identity attributes (such as their DNI or other identifier used with Cl@ve).

Detection Methods for CVE-2025-41064

Indicators of Compromise

• Unusual authentication patterns where multiple users appear to authenticate from the same IP address or session
• Authentication logs showing successful logins without corresponding Cl@ve identity provider verification logs
• Discrepancies between user identity attributes in application logs versus Cl@ve audit trails
• Unexpected administrative actions performed by accounts that typically have limited activity

Detection Strategies

• Monitor authentication logs for anomalies in the Cl@ve authentication flow, including missing or malformed identity assertions
• Implement correlation rules between OpenSIAC authentication events and Cl@ve identity provider logs
• Deploy network monitoring to detect manipulation of authentication traffic between OpenSIAC and Cl@ve endpoints
• Review access patterns for signs of unauthorized impersonation, such as simultaneous sessions from geographically distant locations

Monitoring Recommendations

• Enable detailed logging for all authentication events within OpenSIAC, capturing full request and response data
• Configure alerts for failed authentication attempts followed by successful ones with different identity parameters
• Implement session tracking to identify potential token reuse or session hijacking attempts
• Establish baseline user behavior profiles to detect deviations indicating account compromise

How to Mitigate CVE-2025-41064

Immediate Actions Required

• Review and audit all OpenSIAC deployments that utilize Cl@ve authentication for signs of exploitation
• Consider temporarily disabling Cl@ve authentication until a patch is applied, if feasible
• Implement additional authentication layers or multi-factor authentication as a compensating control
• Restrict network access to OpenSIAC authentication endpoints to trusted IP ranges where possible

Patch Information

Organizations should consult the INCIBE Security Notice for the latest information on available patches and remediation guidance from GTTS Group. Apply vendor-provided security updates as soon as they become available.

Workarounds

• Implement Web Application Firewall (WAF) rules to inspect and validate authentication requests to OpenSIAC
• Deploy reverse proxy configurations that enforce additional authentication checks before requests reach OpenSIAC
• Enable strict TLS certificate validation between OpenSIAC and Cl@ve identity provider endpoints
• Configure network segmentation to limit the blast radius of a potential compromise
• Monitor for and block suspicious authentication patterns at the network perimeter

Organizations should coordinate with GTTS Group and reference the INCIBE security advisory for vendor-recommended workarounds specific to their deployment configuration.