Executive Summary

This vulnerability is an open redirect issue in pgAdmin 4's multi-factor authentication (MFA) flow. Specifically, the MFA validate and register endpoints accepted a user-supplied 'next' parameter without verifying that the redirect target was within the trusted pgAdmin domain. As a result, an authenticated user clicking a specially crafted link with a 'next' parameter pointing to an external, attacker-controlled site could be redirected outside the trusted authentication flow.

The vulnerability does not allow attackers to bypass privileges or gain direct access to pgAdmin or the victim's database. Instead, it enables attackers to increase the success of credential phishing attacks by making the phishing link appear to come from the trusted pgAdmin domain.

The fix involves introducing a helper function that validates redirect URLs to ensure they are either relative paths or absolute URLs pointing to the same host with http(s) schemes. Unsafe redirects are rejected and users are redirected internally instead.

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Impact Analysis

This vulnerability can impact you by increasing the risk of successful credential phishing attacks. Because the redirect appears to come from the trusted pgAdmin domain, attackers can craft links that redirect authenticated users to malicious external sites after login.

While the attacker does not gain direct access to your pgAdmin account or database, the phishing attack could trick you into revealing sensitive credentials or other information on attacker-controlled sites.

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Detection Guidance

This vulnerability involves an open redirect in pgAdmin 4's multi-factor authentication flow where the 'next' parameter can redirect users to external attacker-controlled URLs.

To detect exploitation attempts on your network or system, monitor HTTP requests to the /mfa/validate and /mfa/register endpoints that include a 'next' query or form parameter pointing to external or suspicious URLs.

You can use network monitoring or web server logs to identify such requests. For example, using command-line tools like grep on your web server logs to find suspicious redirects:

• grep -i '/mfa/validate' /path/to/pgadmin/access.log | grep 'next=http'
• grep -i '/mfa/register' /path/to/pgadmin/access.log | grep 'next=http'

Additionally, inspecting logs for unusual redirect URLs or patterns that do not match your pgAdmin host can help identify potential abuse.

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Mitigation Strategies

To mitigate this vulnerability immediately, ensure that your pgAdmin 4 installation is updated to version 9.16 or later, where the fix has been implemented.

The fix introduces a helper function that validates the 'next' parameter to allow only safe internal redirects and rejects unsafe external URLs.

If updating immediately is not possible, consider implementing network-level controls to block or monitor suspicious redirect attempts to external URLs from the MFA endpoints.

Educate users to be cautious of phishing links that exploit this redirect behavior.

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Compliance Impact

This vulnerability is an open redirect in pgAdmin 4's multi-factor authentication flow that can be exploited to redirect authenticated users to attacker-controlled sites, increasing the risk of credential phishing.

While the attacker does not gain direct access to pgAdmin or the victim's database, the increased risk of phishing could potentially lead to unauthorized access to sensitive data.

Such phishing risks may indirectly impact compliance with standards like GDPR and HIPAA, which require protection of personal and sensitive data and mandate measures to prevent unauthorized access.

However, the vulnerability itself is a trusted-domain redirect issue and does not directly expose data or bypass privileges.

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