CVE-2002-0802 in PostgreSQL
Summary
by MITRE
The multibyte support in PostgreSQL 6.5.x with SQL_ASCII encoding consumes an extra character when processing a character that cannot be converted, which could remove an escape character from the query and make the application subject to SQL injection attacks.
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Analysis
by VulDB Data Team • 09/13/2025
The vulnerability described in CVE-2002-0802 represents a critical security flaw in PostgreSQL database systems version 6.5.x that utilizes SQL_ASCII encoding. This issue stems from the database's handling of multibyte character sets and demonstrates how seemingly minor implementation details can create significant security risks. The flaw specifically manifests when the database encounters characters that cannot be properly converted within the SQL_ASCII encoding scheme, leading to unexpected behavior in query processing that can be exploited by malicious actors.
The technical root cause of this vulnerability lies in how PostgreSQL's multibyte character processing handles invalid character sequences. When the database encounters a character that cannot be converted within the SQL_ASCII encoding context, it consumes an additional character from the input stream beyond what is intended. This overconsumption occurs during the character conversion process and specifically affects the handling of escape sequences within SQL queries. The mechanism that should properly parse and validate escape characters becomes compromised, leading to situations where legitimate escape characters are removed or altered during query processing.
The operational impact of this vulnerability extends far beyond simple data corruption or processing errors. When an attacker can manipulate query input to trigger this specific character conversion behavior, they can effectively bypass SQL injection protection mechanisms that rely on proper escape sequence handling. This creates a scenario where malicious input can be injected into database queries without the normal safeguards that would typically prevent such attacks, potentially allowing unauthorized access to database resources, data manipulation, or complete system compromise. The vulnerability essentially creates a backdoor pathway for SQL injection attacks that operates through the database's own character processing logic rather than through traditional input validation failures.
This vulnerability maps directly to CWE-129 and CWE-74 in the Common Weakness Enumeration catalog, representing weaknesses in input validation and improper handling of escape sequences. The attack pattern aligns with ATT&CK technique T1070.004, which involves the use of obfuscated command and scripting interpreters to evade detection while executing malicious code. Organizations using PostgreSQL 6.5.x with SQL_ASCII encoding face significant risk of unauthorized data access and system compromise. The vulnerability demonstrates how encoding-related security issues can create fundamental weaknesses in database security models, particularly when dealing with international character sets and multibyte character support.
Mitigation strategies for this vulnerability require immediate attention and include upgrading to a patched version of PostgreSQL where this specific multibyte character processing issue has been resolved. Organizations should also implement strict input validation mechanisms and avoid using SQL_ASCII encoding in environments where security is a primary concern. Database administrators should consider implementing additional monitoring and logging of query processing to detect unusual character sequence behaviors. The recommended approach involves comprehensive testing of character encoding handling and ensuring that all database applications properly validate and sanitize input data before processing, particularly when dealing with multibyte character sets that may trigger similar conversion issues in other database systems.