CVE-2007-6067 in PostgreSQL
Summary
by MITRE
Algorithmic complexity vulnerability in the regular expression parser in TCL before 8.4.17, as used in PostgreSQL 8.2 before 8.2.6, 8.1 before 8.1.11, 8.0 before 8.0.15, and 7.4 before 7.4.19, allows remote authenticated users to cause a denial of service (memory consumption) via a crafted "complex" regular expression with doubly-nested states.
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Analysis
by VulDB Data Team • 08/03/2019
This vulnerability represents a critical algorithmic complexity issue within the regular expression processing capabilities of TCL versions prior to 8.4.17, which was subsequently embedded in various PostgreSQL database versions. The flaw manifests as a denial of service condition that can be triggered by authenticated remote attackers who craft specific regular expressions containing doubly-nested states. The vulnerability stems from the inefficient handling of regular expression patterns that create exponential growth in computational complexity during parsing operations, leading to excessive memory consumption that can ultimately crash or render the targeted system unavailable.
The technical implementation of this vulnerability exploits the inherent characteristics of regular expression engines that process patterns containing nested quantifiers or complex state transitions. When a regular expression parser encounters doubly-nested states, it can enter into a computationally expensive backtracking process where the number of possible execution paths grows exponentially with the input size. This behavior creates a scenario where a relatively small input string can cause the parser to consume enormous amounts of memory and processing time, effectively exhausting system resources and resulting in a denial of service condition. The vulnerability is particularly dangerous because it can be triggered through database queries that contain crafted regular expressions, making it exploitable through normal database operations.
The operational impact of this vulnerability extends across multiple PostgreSQL versions, affecting releases from 7.4 through 8.2 before their respective patch versions. This widespread exposure means that organizations running these database versions were potentially vulnerable to remote authenticated attacks that could disrupt database services. The vulnerability specifically impacts systems where regular expression processing is utilized, which could include various database functions, text search operations, and application features that rely on pattern matching. The memory consumption aspect makes this particularly problematic for systems with limited resources, as the attack can quickly consume available memory and cause system instability or complete service disruption.
Organizations affected by this vulnerability should prioritize immediate patching of their PostgreSQL installations to versions that include the corrected TCL regular expression parser. The mitigation strategy involves upgrading to PostgreSQL versions 8.2.6, 8.1.11, 8.0.15, and 7.4.19 or later, which contain the necessary fixes to address the algorithmic complexity issue. Additionally, administrators should implement monitoring for unusual memory consumption patterns and consider implementing input validation and sanitization measures to prevent malicious regular expressions from being processed. From a cybersecurity perspective, this vulnerability aligns with CWE-1333 which describes weaknesses in regular expression processing that can lead to resource exhaustion attacks, and it maps to ATT&CK technique T1499.004 related to network denial of service through resource exhaustion. The vulnerability demonstrates the importance of proper input validation and the need for robust algorithmic complexity controls in parsing operations, particularly in database systems where pattern matching is a common operational requirement.