CVE-2000-1165 in syslog-ng
Summary
by MITRE
Balabit syslog-ng allows remote attackers to cause a denial of service (application crash) via a malformed log message that does not have a closing > in the priority specifier.
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Analysis
by VulDB Data Team • 05/28/2018
The vulnerability identified as CVE-2000-1165 affects the Balabit syslog-ng logging daemon, a widely deployed system for collecting and processing log messages in Unix and Linux environments. This issue represents a classic buffer overflow or parsing error that occurs when the system encounters malformed input data, specifically log messages that lack proper termination characters. The syslog-ng daemon serves as a critical component in network security infrastructure, handling log aggregation from various network devices, servers, and applications, making it a prime target for attackers seeking to disrupt system operations.
The technical flaw manifests in the priority specifier parsing mechanism of syslog-ng where the application expects a closing angle bracket character to properly terminate the priority field in log messages. When a remote attacker crafts a malicious log message that omits this required closing character, the parsing routine fails to properly handle the malformed input, leading to an application crash. This vulnerability operates at the protocol level where syslog-ng processes incoming messages according to the standard syslog format, which specifies that priority values should be enclosed in angle brackets. The absence of this closing bracket causes the application to either enter an infinite loop, consume excessive memory resources, or experience a segmentation fault that results in process termination.
The operational impact of this vulnerability extends beyond simple service disruption as it can be exploited to create persistent denial of service conditions within network monitoring and security operations centers. When syslog-ng crashes, it stops processing legitimate log messages, creating gaps in security monitoring and audit trails that could mask malicious activities. The vulnerability is particularly dangerous in environments where syslog-ng serves as the central logging daemon for security information and event management systems, as it can effectively disable crucial logging capabilities. Attackers can exploit this weakness by sending a single malformed message to any system running vulnerable syslog-ng versions, causing immediate service disruption without requiring authentication or complex attack vectors.
Mitigation strategies for CVE-2000-1165 should focus on immediate patching of affected syslog-ng installations, as the vulnerability was addressed through software updates that improved input validation and error handling mechanisms. Network administrators should implement input filtering at network boundaries to prevent malformed log messages from reaching syslog-ng servers, particularly in environments where external systems may not properly format their log data. The vulnerability aligns with CWE-121, which covers stack-based buffer overflow conditions, and demonstrates characteristics similar to those found in ATT&CK technique T1499.004, specifically the use of application or system exploitation for denial of service. Organizations should also consider implementing redundant logging systems and monitoring for unusual syslog-ng process restarts that could indicate exploitation attempts, while ensuring proper network segmentation to limit the potential impact of such attacks on critical infrastructure components.