CVE-2026-3432: SimStudio Auth Bypass Vulnerability

CVE-2026-3432 Overview

CVE-2026-3432 is a critical authorization bypass vulnerability in SimStudio versions below 0.5.74. The /api/auth/oauth/token endpoint contains a code path that bypasses all authorization checks when provided with credentialAccountUserId and providerId parameters. An unauthenticated attacker can retrieve OAuth access tokens for any user by supplying their user ID and a provider name, effectively stealing credentials to third-party services.

Critical Impact

This vulnerability enables unauthenticated attackers to steal OAuth access tokens for any user account, potentially compromising linked third-party service credentials and enabling account takeover across multiple platforms.

Affected Products

• SimStudio versions below 0.5.74

Discovery Timeline

• 2026-03-02 - CVE CVE-2026-3432 published to NVD
• 2026-03-02 - Last updated in NVD database

Technical Details for CVE-2026-3432

Vulnerability Analysis

This vulnerability is classified as CWE-862 (Missing Authorization), representing a fundamental authentication and authorization bypass flaw. The /api/auth/oauth/token endpoint fails to properly validate whether the requesting party is authorized to retrieve OAuth tokens for a given user account.

When a request is made to the vulnerable endpoint with specific parameters (credentialAccountUserId and providerId), the application enters a code path that completely bypasses authorization checks. This allows an unauthenticated remote attacker to enumerate user IDs and retrieve valid OAuth access tokens that were issued to those users for connected third-party services.

The vulnerability is particularly severe because OAuth tokens typically grant access to external services such as cloud storage, code repositories, social media accounts, or enterprise applications. Compromising these tokens extends the impact far beyond the SimStudio application itself.

Root Cause

The root cause is a missing authorization check in the OAuth token retrieval logic. The application fails to verify that the authenticated (or in this case, unauthenticated) user has permission to access OAuth credentials belonging to other user accounts. This is a classic broken access control vulnerability where object-level authorization is not enforced.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying the vulnerable SimStudio instance exposed to the network
2. Sending crafted requests to the /api/auth/oauth/token endpoint
3. Supplying target credentialAccountUserId values (which may be enumerable or guessable)
4. Specifying known providerId values for connected OAuth services
5. Receiving valid OAuth access tokens that can be used to access third-party services on behalf of the victim user

The attack is trivial to execute once the vulnerable endpoint is identified, as it only requires knowledge of user IDs and provider names, both of which may be predictable or discoverable through other means.

Detection Methods for CVE-2026-3432

Indicators of Compromise

• Unusual or high-volume requests to /api/auth/oauth/token endpoint from unauthenticated sources
• API requests containing credentialAccountUserId parameters with sequential or enumerated values
• Access to OAuth token endpoints from IP addresses not associated with legitimate user activity
• Third-party service access logs showing authentication from unexpected locations or IP addresses

Detection Strategies

• Implement API request monitoring to detect unauthenticated access attempts to the OAuth token endpoint
• Configure web application firewall (WAF) rules to flag requests to /api/auth/oauth/token without valid session cookies
• Monitor for parameter enumeration patterns in credentialAccountUserId values
• Enable detailed logging on authentication and OAuth endpoints for forensic analysis

Monitoring Recommendations

• Set up alerting for failed or anomalous OAuth token requests in application logs
• Monitor connected third-party services for signs of unauthorized access using compromised tokens
• Review access logs for the vulnerable endpoint to identify potential exploitation attempts
• Implement rate limiting on authentication-related endpoints to slow enumeration attacks

How to Mitigate CVE-2026-3432

Immediate Actions Required

• Upgrade SimStudio to version 0.5.74 or later immediately
• Audit access logs for the /api/auth/oauth/token endpoint to identify potential compromise
• Revoke and rotate all OAuth tokens that may have been exposed
• Review connected third-party service accounts for signs of unauthorized access

Patch Information

The vulnerability has been addressed in SimStudio version 0.5.74 and later. Organizations should upgrade to the latest available version. For detailed technical information about this vulnerability, refer to the Tenable Security Research Advisory.

Workarounds

• Restrict network access to the SimStudio application to trusted IP ranges only
• Implement a reverse proxy or WAF rule to block unauthenticated requests to /api/auth/oauth/token
• Disable OAuth integrations temporarily if they are not critical to operations
• Monitor and alert on any requests to the vulnerable endpoint until patching is complete

# Example: Block access to vulnerable endpoint using nginx
location /api/auth/oauth/token {
    # Require authentication or restrict to internal IPs
    allow 10.0.0.0/8;
    allow 192.168.0.0/16;
    deny all;
}