CVE-2011-1489 in rsyslog
Summary
by MITRE
A memory leak in rsyslog before 5.7.6 was found in the way deamon processed log messages were logged when multiple rulesets were used and some output batches contained messages belonging to more than one ruleset. A local attacker could cause denial of the rsyslogd daemon service via a log message belonging to more than one ruleset.
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Analysis
by VulDB Data Team • 02/02/2025
The vulnerability identified as CVE-2011-1489 represents a critical memory management flaw in the rsyslog daemon software that affected versions prior to 5.7.6. This memory leak occurred specifically within the daemon's processing logic when handling log messages that belonged to multiple rulesets simultaneously. The issue manifested when the system encountered output batches containing messages from different rulesets, creating a scenario where the memory allocation and deallocation processes failed to properly manage resources. The root cause lies in the improper handling of memory references during the ruleset processing phase, where allocated memory was not correctly released back to the system after processing complex message batches.
The technical exploitation of this vulnerability leveraged the daemon's behavior when processing log messages that spanned multiple rulesets, creating a condition where memory consumption would progressively increase without proper garbage collection. This memory leak directly impacts the daemon's operational stability and resource utilization, as the continuous accumulation of unreleased memory fragments would eventually exhaust available system resources. The vulnerability is classified under CWE-401 as a weakness related to improper management of memory allocation and deallocation, specifically manifesting as a memory leak in the system's logging infrastructure.
From an operational perspective, this vulnerability creates a significant risk for systems relying on rsyslog for centralized logging operations, particularly in environments where multiple rulesets are configured to handle different types of log messages. A local attacker could exploit this weakness by crafting specially formatted log messages that would trigger the memory leak condition, ultimately leading to a denial of service scenario where the rsyslogd daemon becomes unresponsive or terminates unexpectedly. The impact extends beyond simple service disruption as it affects the entire logging infrastructure, potentially causing loss of critical system logs and compromising security monitoring capabilities.
The attack vector for CVE-2011-1489 is particularly concerning because it requires only local access to the system and can be executed through normal log message processing operations. This makes it difficult to detect and prevent as it operates within legitimate system behavior patterns. The vulnerability aligns with ATT&CK technique T1499.004 which involves resource exhaustion through service denial, and specifically targets the availability aspect of the CIA triad. Organizations using rsyslog in production environments should prioritize immediate patching to version 5.7.6 or later, as the memory leak can be exploited to cause persistent service disruption. Mitigation strategies should include monitoring system memory usage patterns and implementing automated restart mechanisms for the rsyslog daemon to prevent extended service outages.
The broader implications of this vulnerability highlight the critical importance of proper memory management in system daemons and logging services, where resource exhaustion can lead to complete service failure. The flaw demonstrates how seemingly routine processing operations can become exploitation vectors when memory management is inadequate. This vulnerability serves as a reminder of the need for comprehensive testing of edge cases in logging systems, particularly those involving complex rule-based processing. Organizations should implement regular vulnerability assessments of their logging infrastructure and maintain up-to-date security patches to prevent similar memory management issues from compromising system availability and security monitoring capabilities.