CVE-2015-6817 in PgBouncer
Summary
by MITRE
PgBouncer 1.6.x before 1.6.1, when configured with auth_user, allows remote attackers to gain login access as auth_user via an unknown username.
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Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2015-6817 affects PgBouncer versions 1.6.x prior to 1.6.1 and represents a significant authentication bypass flaw that undermines the security posture of database proxy configurations. This issue specifically manifests when PgBouncer is configured with the auth_user parameter, creating a scenario where remote attackers can exploit a flaw in the authentication mechanism to gain unauthorized access to database systems. The vulnerability stems from an improper handling of username validation during the authentication process, allowing malicious actors to leverage an unknown username to impersonate the configured auth_user account. The flaw essentially creates a backdoor authentication path that bypasses normal security controls, potentially enabling attackers to establish database connections with elevated privileges.
The technical implementation of this vulnerability involves a weakness in the authentication flow where PgBouncer fails to properly validate or sanitize username inputs when the auth_user parameter is active. This allows an attacker to submit a crafted username that triggers an authentication bypass condition, effectively granting access to the database as the configured auth_user rather than the intended user. The vulnerability operates at the application layer and can be exploited remotely without requiring prior authentication credentials. From a cybersecurity perspective, this represents a classic case of inadequate input validation and authentication flow control, which aligns with CWE-287 (Improper Authentication) and CWE-20 (Improper Input Validation). The flaw demonstrates a failure in the principle of least privilege and authentication integrity, as the system does not properly verify that the requesting user has legitimate authorization to assume the target authentication identity.
The operational impact of CVE-2015-6817 extends beyond simple unauthorized access, potentially enabling attackers to perform database operations, extract sensitive information, modify data, or establish persistent access to backend database systems. Organizations using PgBouncer with auth_user configuration are particularly vulnerable, as this flaw can be exploited by attackers with minimal reconnaissance requirements. The vulnerability can facilitate data exfiltration, privilege escalation, and may serve as a stepping stone for further attacks within the database infrastructure. From an attacker's perspective, this represents a low-effort, high-impact vector that can be automated and scaled against multiple systems. The vulnerability also creates challenges for security monitoring and incident response, as legitimate authentication attempts may be obscured by malicious activity. This aligns with ATT&CK technique T1078 (Valid Accounts) and T1566 (Phishing) where the vulnerability enables unauthorized access through legitimate authentication mechanisms.
Mitigation strategies for CVE-2015-6817 primarily involve immediate patching of PgBouncer to version 1.6.1 or later, which addresses the authentication bypass flaw through proper username validation and authentication flow control. Organizations should also review their PgBouncer configurations to minimize the use of auth_user parameter where possible, or implement additional authentication layers such as SSL client certificates or IP-based access controls. Network segmentation and firewall rules should be implemented to restrict access to PgBouncer instances to trusted networks only, reducing the attack surface. Security monitoring should be enhanced to detect unusual authentication patterns or attempts to access the system using unexpected usernames. Additionally, organizations should conduct comprehensive vulnerability assessments of their database infrastructure to identify similar authentication flaws and implement proper principle of least privilege controls. Regular security updates and patch management processes should be enforced to prevent similar vulnerabilities from being introduced through outdated software components. The vulnerability highlights the importance of proper authentication design and input validation in database proxy systems, emphasizing that authentication mechanisms must be robust against both known and unknown attack vectors.