CVE-2011-1488 in rsyslog
Summary
by MITRE
A memory leak in rsyslog before 5.7.6 was found in the way deamon processed log messages are logged when $RepeatedMsgReduction was enabled. A local attacker could use this flaw to cause a denial of the rsyslogd daemon service by crashing the service via a sequence of repeated log messages sent within short periods of time.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/02/2025
The vulnerability identified as CVE-2011-1488 represents a critical memory management flaw in the rsyslog daemon software that affected versions prior to 5.7.6. This issue specifically manifests when the daemon processes log messages with the $RepeatedMsgReduction configuration parameter enabled, which is designed to reduce storage consumption by compressing repeated log entries. The memory leak occurs during the processing of repeated messages, creating a condition where allocated memory is not properly released back to the system. This flaw demonstrates a classic example of improper resource management that violates established security principles and can be exploited to compromise system availability.
The technical implementation of this vulnerability stems from how rsyslog handles memory allocation when processing repeated log entries under the $RepeatedMsgReduction setting. When multiple identical or similar log messages are received in rapid succession, the daemon allocates memory to store and process these messages but fails to properly deallocate this memory upon completion of processing. This memory allocation pattern creates a progressive accumulation of unused memory blocks that cannot be reclaimed by the system, leading to a gradual degradation of system resources. The flaw operates at the application level within the rsyslog daemon's message processing loop, specifically affecting the internal data structures used for tracking repeated messages and their reduction mechanisms.
From an operational perspective, this vulnerability creates a significant denial-of-service risk that can be exploited by local attackers with minimal privileges. The attack vector requires only the ability to send repeated log messages to the rsyslog daemon, which can be accomplished through various means including crafting malicious log entries or exploiting applications that generate high volumes of repeated messages. The impact of this vulnerability extends beyond simple service disruption, as it can lead to complete daemon crashes and system instability. The memory leak can occur rapidly when sequences of repeated messages are sent within short time intervals, making it particularly dangerous in environments where log volume is high or where automated applications generate repetitive logging patterns. This vulnerability directly impacts the availability and reliability of system logging services that are critical for security monitoring and forensic analysis.
The security implications of CVE-2011-1488 align with several common weakness enumerations including CWE-401, which describes improper cleanup of memory allocation, and CWE-119, which addresses memory corruption vulnerabilities. The attack pattern follows typical denial-of-service methodologies found in the MITRE ATT&CK framework under the technique of "Resource Exhaustion" and "Execution Guardrails" where attackers can manipulate system resources to cause service disruption. Organizations utilizing rsyslog for system logging are particularly vulnerable since log aggregation and monitoring are fundamental to security operations. The vulnerability's exploitation demonstrates the importance of proper memory management practices in security-critical applications and highlights the need for regular security updates and patch management procedures. System administrators should prioritize updating rsyslog to version 5.7.6 or later to remediate this vulnerability and prevent potential service disruptions that could impact security monitoring capabilities and system availability.