CVE-2007-6437 in Syslog-ng Open Source Edition
Summary
by MITRE
Balabit syslog-ng 2.0.x before 2.0.6 and 2.1.x before 2.1.8 allows remote attackers to cause a denial of service (crash) via a message with a timestamp that does not contain a trailing space, which triggers a NULL pointer dereference.
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Analysis
by VulDB Data Team • 08/02/2019
The vulnerability identified as CVE-2007-6437 represents a critical denial of service flaw affecting Balabit syslog-ng versions prior to 2.0.6 and 2.1.8. This issue manifests when the syslog-ng daemon processes log messages containing timestamps that lack a trailing space character, leading to a NULL pointer dereference condition that ultimately crashes the application. The vulnerability specifically targets the timestamp parsing mechanism within the syslog-ng logging daemon, which is widely deployed across enterprise networks for centralized log management and security monitoring. Given syslog-ng's role as a fundamental component in many security infrastructure deployments, this flaw presents a significant operational risk that could disrupt critical logging services and potentially mask other security incidents.
The technical root cause of this vulnerability lies in improper input validation within the timestamp parsing routine of the syslog-ng daemon. When processing log messages, the application expects timestamp formats to include specific formatting conventions including trailing spaces to delineate time components. However, when encountering messages where timestamps lack this trailing space, the parsing logic fails to properly handle the NULL pointer reference, resulting in an application crash. This behavior aligns with CWE-476, which describes NULL pointer dereference vulnerabilities, and demonstrates how inadequate input sanitization can lead to application instability. The flaw operates at the application layer and requires remote exploitation through crafted log messages sent to the vulnerable syslog-ng instance, making it particularly dangerous in networked environments where syslog-ng receives messages from multiple sources.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise security monitoring capabilities. Organizations relying on syslog-ng for log aggregation and security event correlation face significant risk when this vulnerability is exploited, as the denial of service could occur without detection and may be used to obscure malicious activities. The vulnerability's remote exploitation capability means that attackers could target systems from external networks, potentially disrupting log collection services at critical infrastructure points. This attack vector aligns with ATT&CK technique T1499.004, which covers network disruption attacks, and represents a significant threat to operational continuity in security operations centers that depend on continuous log flow for threat detection and incident response activities.
Mitigation strategies for CVE-2007-6437 primarily involve immediate deployment of patched versions of syslog-ng, specifically versions 2.0.6 and 2.1.8 or later. Organizations should also implement network segmentation and access controls to limit exposure of syslog-ng services to untrusted networks. Additional protective measures include deploying monitoring solutions to detect unusual crash patterns and implementing redundant logging systems to maintain operational continuity. Security teams should conduct comprehensive vulnerability assessments to identify all instances of affected syslog-ng versions within their environments and establish procedures for rapid patch deployment. The vulnerability serves as a reminder of the importance of input validation in security-critical applications and the necessity of maintaining up-to-date software versions to protect against known exploitation vectors.