CVE-2007-4772 in PostgreSQL
Summary
by MITRE
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 context-dependent attackers to cause a denial of service (infinite loop) via a crafted regular expression.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/03/2019
The vulnerability identified as CVE-2007-4772 represents a critical security flaw in the regular expression parsing functionality of Tcl versions prior to 8.4.17. This issue specifically affects PostgreSQL database systems where the Tcl regular expression engine is utilized for pattern matching operations. The vulnerability stems from inadequate input validation and processing within the regular expression parser, creating a condition where maliciously crafted regular expressions can trigger infinite loop scenarios. This affects multiple PostgreSQL versions including 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, indicating a widespread impact across several database server releases. The vulnerability operates through a context-dependent attack vector, meaning that the malicious input must be carefully constructed to exploit the specific parsing behavior of the regular expression engine.
The technical implementation of this vulnerability involves the regular expression parser's handling of certain pattern constructs that lead to exponential backtracking behavior. When processing malformed regular expressions, the parser enters into an infinite loop state where it repeatedly evaluates the same pattern matches without making progress toward completion. This occurs because the parser fails to implement proper bounds checking or timeout mechanisms for regular expression evaluation. The flaw can be categorized under CWE-121 as a buffer overflow condition or more specifically as a CWE-129 as an improper limitation of a recognized maximum. The vulnerability demonstrates a classic example of how regular expression engines can be exploited through carefully crafted inputs that cause computational complexity to spiral beyond reasonable bounds, effectively consuming system resources and rendering the service unavailable.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can be leveraged to create significant system instability and resource exhaustion. Attackers can craft regular expressions that cause the database server to consume excessive CPU cycles and memory resources, potentially leading to complete system unresponsiveness. In database environments where regular expressions are frequently used for data validation, pattern matching, or text processing operations, this vulnerability can be particularly dangerous as it can be triggered through normal database operations. The attack requires minimal privileges and can be executed through standard database query interfaces, making it a high-risk vulnerability for database administrators. This aligns with ATT&CK technique T1499.004 for network denial of service and represents a significant threat to database availability and integrity.
Mitigation strategies for CVE-2007-4772 focus on immediate patching of affected systems, with the primary solution being the upgrade to Tcl 8.4.17 or later versions that contain fixed regular expression parsers. Database administrators should prioritize updating their PostgreSQL installations to versions that incorporate the patched Tcl libraries, particularly for the affected versions mentioned in the vulnerability description. Additionally, implementing input validation and sanitization measures at the application level can help prevent malicious regular expressions from reaching the database engine. Organizations should consider implementing timeouts for regular expression processing operations and monitoring for unusual resource consumption patterns that might indicate exploitation attempts. Network-level controls such as rate limiting and input filtering can provide additional defense-in-depth measures, though these are secondary to the primary patching requirement. The vulnerability highlights the importance of regularly updating third-party libraries and components within database systems, as vulnerabilities in underlying libraries can have cascading effects across multiple applications and services that depend on them.