CVE-2015-4054 in PgBouncer
Summary
by MITRE
PgBouncer before 1.5.5 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) by sending a password packet before a startup packet.
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Analysis
by VulDB Data Team • 12/07/2022
PgBouncer version 1.5.4 and earlier contains a critical denial of service vulnerability that stems from improper handling of authentication packets in the connection management process. This vulnerability manifests when a remote attacker sends a password packet before the expected startup packet, triggering a NULL pointer dereference that ultimately results in the application crashing. The flaw exists in the protocol parsing logic where the system fails to validate the sequence of incoming packets before attempting to process authentication credentials.
The technical implementation of this vulnerability resides in the connection initialization phase where PgBouncer expects a specific packet order for proper authentication flow. When a password packet is received without the preceding startup packet, the internal state management becomes inconsistent, leading to a NULL pointer dereference in the authentication handler. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. The crash occurs because the application attempts to access memory locations that have not been properly initialized or allocated, creating an unhandled exception that terminates the process.
From an operational perspective, this vulnerability presents a significant risk to database availability and system stability. Attackers can exploit this weakness to repeatedly crash PgBouncer instances, effectively denying legitimate users access to database resources. The impact extends beyond simple service disruption as it can lead to cascading failures in applications that depend on PgBouncer for connection pooling. The vulnerability is particularly concerning in production environments where database connectivity is critical and any disruption can result in substantial business impact. This type of attack pattern aligns with ATT&CK technique T1499.004 which covers network denial of service attacks targeting database services.
The mitigation strategy for this vulnerability requires immediate upgrade to PgBouncer version 1.5.5 or later where the packet sequence validation has been implemented. Organizations should also consider implementing network-level controls to restrict access to PgBouncer ports and monitor for anomalous packet sequences. Additional defensive measures include configuring intrusion detection systems to identify suspicious authentication packet patterns and implementing proper connection rate limiting to prevent abuse of the vulnerability. The fix addresses the root cause by introducing proper packet ordering validation and ensuring that authentication handlers only process packets when the connection state is properly initialized. Organizations should also conduct regular security assessments to identify similar vulnerabilities in other database connection tools and middleware components that may exhibit similar packet processing flaws.