CVE-2002-1642 in PostgreSQL
Summary
by MITRE
PostgreSQL 7.2.1 and 7.2.2 allows local users to delete transaction log (pg_clog) data and cause a denial of service (data loss) via the VACUUM command.
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Analysis
by VulDB Data Team • 09/03/2025
The vulnerability described in CVE-2002-1642 represents a critical security flaw in PostgreSQL database systems version 7.2.1 and 7.2.2 that enables local users to manipulate transaction log data through the VACUUM command. This issue stems from insufficient access controls and validation mechanisms within the database engine's transaction management system. The vulnerability specifically targets the pg_clog directory which contains critical transaction status information essential for database consistency and recovery operations. When exploited, this flaw allows attackers with local system access to deliberately remove or corrupt transaction log entries, potentially leading to complete data loss and system unavailability.
The technical implementation of this vulnerability occurs through the improper handling of the VACUUM command execution path in PostgreSQL's backend processes. The VACUUM command is designed to reclaim storage occupied by dead tuples and update statistics, but in these vulnerable versions it fails to properly validate file access permissions when interacting with the pg_clog directory. This allows local users to manipulate the transaction log files directly through the command interface, bypassing normal database security mechanisms. The flaw operates at the file system level where the database engine performs operations on transaction status files without adequate verification of the requesting user's privileges or the integrity of the operations being performed. This represents a classic case of insufficient input validation and inadequate privilege separation between database operations and file system interactions.
The operational impact of this vulnerability extends beyond simple denial of service to encompass complete data integrity compromise and potential system instability. When transaction log data is deleted or corrupted, the database system loses critical information about transaction states, which can lead to cascading failures in database operations. The pg_clog directory maintains essential metadata about committed and aborted transactions that PostgreSQL relies upon for maintaining ACID properties and database consistency. The deletion of this data can cause the database to enter an inconsistent state where it cannot properly resolve transaction dependencies, leading to data corruption or complete system failure. This vulnerability particularly affects systems where local users might have access to database processes or where privilege escalation is possible, as it requires only local access to exploit.
Mitigation strategies for this vulnerability should focus on immediate patching and system hardening measures. Organizations must upgrade to PostgreSQL versions that address this specific flaw, typically versions 7.2.3 and later which contain proper access controls and validation mechanisms for transaction log operations. System administrators should implement strict access controls to prevent unauthorized local access to database systems and ensure that only privileged users can execute administrative commands including VACUUM. The implementation of proper file system permissions and audit logging for database operations can help detect and prevent exploitation attempts. Additionally, regular database backups and recovery testing should be maintained to ensure that data loss can be recovered even if such vulnerabilities are exploited. This vulnerability aligns with CWE-276 which addresses improper file permissions and privilege management, and relates to ATT&CK techniques involving privilege escalation and data destruction through file system manipulation. Organizations should also consider implementing database activity monitoring to detect anomalous VACUUM operations that might indicate exploitation attempts.