CVE-2026-6665 PgBouncer SCRAM Buffer Overflow Vulnerability

CVE-2026-6665 describes a buffer overflow vulnerability within the SCRAM (Salted Challenge Response Authentication Mechanism) implementation of PgBouncer, a lightweight connection pooler for PostgreSQL. An attacker could exploit this vulnerability by sending a specially crafted authentication request to PgBouncer, potentially leading to arbitrary code execution on the affected system. The Microsoft Security Response Center (MSRC) published information about this vulnerability. Successful exploitation could allow an attacker to gain unauthorized access to the database server and compromise sensitive data. Due to the nature of buffer overflows, exploitation can result in service disruption or complete system takeover.

Attack Chain

1. An attacker identifies a vulnerable PgBouncer instance.
2. The attacker initiates a connection to the PgBouncer instance.
3. The attacker begins the SCRAM authentication process.
4. The attacker sends a malicious SCRAM authentication message containing an oversized payload.
5. The oversized payload overflows the allocated buffer in PgBouncer’s memory.
6. The buffer overflow overwrites adjacent memory regions, potentially including executable code.
7. The attacker gains control of the execution flow by overwriting critical data or function pointers.
8. The attacker executes arbitrary code on the server, potentially gaining access to sensitive data or escalating privileges.

Impact

Successful exploitation of CVE-2026-6665 allows a remote attacker to execute arbitrary code on the system running the vulnerable PgBouncer instance. This could lead to complete system compromise, data exfiltration, or denial of service. The impact of successful exploitation is high, as it can lead to unauthorized access to sensitive data, disruption of services, and potential financial losses.

Recommendation

• Deploy the Sigma rules provided below to your SIEM to detect exploitation attempts.
• Monitor network traffic for unusually large SCRAM authentication messages targeting PgBouncer instances (see network_connection rule).
• Investigate and patch vulnerable PgBouncer instances immediately to prevent potential exploitation.