Executive Summary

The Debian project has released an important security update to address a high-severity SQL injection vulnerability, CVE-2025-12819, in PgBouncer, a popular connection pooling utility for PostgreSQL databases. The flaw, rated 8.1 on the CVSS scale, allows a remote, unauthenticated attacker to execute arbitrary SQL commands on the underlying database server during the authentication handshake. This could lead to data compromise, privilege escalation, or denial of service. The vulnerability has been patched in PgBouncer version 1.25.1, and Debian has issued an update for its 'bullseye' stable release. Administrators using the affected software are strongly advised to apply the patches immediately.

Vulnerability Details

The vulnerability exists in how PgBouncer's auth_query connection handler processes the search_path parameter. During the authentication phase, a remote, unauthenticated attacker can send a specially crafted StartupMessage containing a malicious search_path. This parameter is not properly sanitized, allowing the attacker to inject arbitrary SQL commands. These commands are then executed with the privileges of the PgBouncer user on the PostgreSQL database server.

This is a classic SQL injection vulnerability, but it is particularly dangerous because it occurs pre-authentication, requiring only network access to the PgBouncer service.

Affected Systems

• PgBouncer: Versions prior to 1.25.1
• Debian 11 'bullseye': PgBouncer versions prior to 1.15.0-1+deb11u2

Any system using PgBouncer to manage PostgreSQL connections may be at risk if running a vulnerable version.

Exploitation Status

As of the security advisory on December 27, 2025, there were no known public exploits or reports of active exploitation in the wild. However, given the detailed nature of the disclosure and the high severity of the flaw, it is likely that threat actors will develop exploits. Proactive patching is essential.

Impact Assessment

Successful exploitation of CVE-2025-12819 could have a severe impact on the integrity and confidentiality of the connected PostgreSQL database. An attacker could:

• Execute arbitrary SQL queries to read, modify, or delete any data in the database (T1005 - Data from Local System).
• Escalate privileges within the database, potentially gaining administrative control.
• In some PostgreSQL configurations, execute operating system commands, leading to a full compromise of the database server (T1059 - Command and Scripting Interpreter).
• Cause a denial of service by executing resource-intensive queries.

Detection Methods

1. Version Checking: The most reliable detection method is to check the version of the installed PgBouncer package. On Debian systems, this can be done with dpkg -l | grep pgbouncer.
2. Database Log Analysis: Monitor PostgreSQL logs for unusual or malformed queries originating from the PgBouncer connection user. Look for queries that include unexpected SET search_path commands or other suspicious SQL syntax. This is a form of D3-DA: Database Analysis.
3. Network Monitoring: Analyze traffic to the PgBouncer port (default 6432) for malformed StartupMessages, although this may require deep packet inspection.

Remediation Steps

1. Upgrade PgBouncer: The primary and most effective remediation is to upgrade to a patched version.
   • For Debian 11 'bullseye', upgrade to version 1.15.0-1+deb11u2 or later by running sudo apt-get update && sudo apt-get install pgbouncer.
   • For other systems, upgrade to PgBouncer version 1.25.1 or later. This is a direct application of D3-SU: Software Update.
2. Restrict Network Access: As a defense-in-depth measure, ensure that the PgBouncer service is not exposed to untrusted networks. Use firewall rules to restrict access to only the specific application servers that need to connect to it. This aligns with D3-NI: Network Isolation.
3. Principle of Least Privilege: Ensure that the database user account used by PgBouncer has the minimum necessary privileges to perform its function. This can limit the impact of a successful SQL injection attack.