CVE-2026-25649: Traccar OAuth 2.0 Auth Bypass Vulnerability

CVE-2026-25649 Overview

CVE-2026-25649 is an Open Redirect vulnerability affecting the Traccar open-source GPS tracking system. Authenticated users can exploit this flaw to steal OAuth 2.0 authorization codes by manipulating the redirect_uri parameter in OIDC-related endpoints. Because the application fails to validate this parameter against a whitelist of allowed redirect URIs, attackers can redirect authorization codes to attacker-controlled URLs, potentially enabling account takeover on any OAuth-integrated application.

Critical Impact

Authenticated attackers can intercept OAuth 2.0 authorization codes and gain unauthorized access to user accounts on OAuth-integrated applications, leading to complete account takeover.

Affected Products

• Traccar GPS Tracking System versions up to and including 6.11.1
• All Traccar installations utilizing OIDC authentication
• OAuth-integrated applications connected to vulnerable Traccar instances

Discovery Timeline

• 2026-02-23 - CVE-2026-25649 published to NVD
• 2026-02-26 - Last updated in NVD database

Technical Details for CVE-2026-25649

Vulnerability Analysis

This vulnerability exists in two OIDC (OpenID Connect) related endpoints within Traccar's authentication flow. The core issue stems from insufficient validation of the redirect_uri parameter during the OAuth 2.0 authorization process. When a user authenticates through the OIDC flow, the application generates an authorization code that is sent back to the client application via the specified redirect URI.

The vulnerability allows authenticated attackers to craft malicious authentication requests containing attacker-controlled redirect URIs. Since no whitelist validation occurs, the authorization server will redirect the user—along with the valid authorization code—to the attacker's server. The attacker can then exchange this stolen authorization code for access tokens, effectively impersonating the victim.

This vulnerability is classified under CWE-601 (URL Redirection to Untrusted Site) and CWE-352 (Cross-Site Request Forgery), as the attack requires user interaction through a crafted link and exploits improper redirect URI validation.

Root Cause

The root cause is the absence of redirect URI validation against a predefined whitelist of allowed callback URLs. According to OAuth 2.0 security best practices (RFC 6749), authorization servers must validate the redirect_uri parameter against pre-registered client redirect URIs. Traccar's OIDC endpoints fail to implement this critical security control, accepting arbitrary redirect destinations without verification.

Attack Vector

The attack requires network access and involves an authenticated attacker crafting a malicious OAuth authorization URL with a manipulated redirect_uri parameter pointing to an attacker-controlled server. The attacker must then convince a victim to click the malicious link. When the victim authenticates, the authorization code is redirected to the attacker's server instead of the legitimate application. The attacker can then use this authorization code to complete the OAuth flow and gain access to the victim's account.

The attack typically follows this sequence:

1. Attacker identifies the vulnerable OIDC endpoints in Traccar
2. Attacker constructs a malicious authorization URL with redirect_uri pointing to their server
3. Victim clicks the link and authenticates with their credentials
4. Authorization code is sent to the attacker-controlled URL
5. Attacker exchanges the code for access tokens and impersonates the victim

Detection Methods for CVE-2026-25649

Indicators of Compromise

• Unexpected OAuth authorization requests with unusual redirect_uri values in application logs
• Authorization codes being issued to external or unrecognized domains
• Failed token exchange attempts following successful authorization (attacker may have already used the code)
• User reports of unexpected account access or suspicious activity on OAuth-integrated applications

Detection Strategies

• Monitor OAuth authorization endpoint logs for redirect_uri parameters pointing to external or non-whitelisted domains
• Implement alerting on authorization code issuance to unusual or first-seen redirect URIs
• Analyze network traffic for OAuth flows redirecting to suspicious external endpoints
• Review authentication logs for patterns of authorization codes being issued but not redeemed by legitimate clients

Monitoring Recommendations

• Enable detailed logging for all OIDC-related endpoints and OAuth authorization flows
• Configure SIEM rules to detect anomalous redirect URI patterns in OAuth requests
• Monitor for spikes in authorization code generation that may indicate exploitation attempts
• Implement user behavior analytics to detect account access from unusual locations or devices following OAuth authentication

How to Mitigate CVE-2026-25649

Immediate Actions Required

• Review and audit all OIDC and OAuth configurations in Traccar deployments
• Consider disabling OIDC authentication until a patch becomes available if feasible
• Implement network-level controls to restrict access to OIDC endpoints to trusted networks only
• Educate users about phishing attacks involving malicious OAuth authorization links

Patch Information

As of the publication date, it is unclear whether a fix is available from the vendor. Organizations should monitor the Traccar GitHub Security Advisory for updates regarding patches and remediation guidance. Upgrade to the latest Traccar version as soon as a security fix is released.

Workarounds

• Deploy a reverse proxy or web application firewall (WAF) in front of Traccar to validate redirect_uri parameters against a whitelist of allowed domains
• Restrict network access to OIDC endpoints using firewall rules or access control lists
• Implement additional authentication factors for OAuth-integrated applications to reduce account takeover risk
• Consider using alternative authentication mechanisms until the vulnerability is patched

# Example: Nginx reverse proxy configuration to whitelist redirect URIs
# Add to your Nginx server block protecting Traccar

location ~ ^/(api/session/oidc|oauth) {
    # Block requests with redirect_uri containing external domains
    if ($arg_redirect_uri !~ "^https://your-trusted-domain\.com") {
        return 403;
    }
    proxy_pass http://traccar_backend;
}