CVE-2013-4758 in rsyslog
Summary
by MITRE
Double free vulnerability in the writeDataError function in the ElasticSearch plugin (omelasticsearch) in rsyslog before 7.4.2 and before 7.5.2 devel, when errorfile is set to local logging, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted JSON response.
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Analysis
by VulDB Data Team • 03/27/2019
The CVE-2013-4758 vulnerability represents a critical double free error in the rsyslog omelasticsearch plugin component, affecting versions prior to 7.4.2 and 7.5.2 development releases. This vulnerability specifically manifests within the writeDataError function when the errorfile parameter is configured for local logging operations. The flaw exists in the memory management handling of dynamically allocated resources within the Elasticsearch plugin module, creating a scenario where the same memory block can be freed twice during error processing operations. Such memory corruption vulnerabilities are particularly dangerous as they can lead to unpredictable behavior including application crashes, denial of service conditions, and in some cases arbitrary code execution.
The technical exploitation of this vulnerability requires a remote attacker to craft a specially formatted JSON response that triggers the problematic writeDataError function path. When rsyslog processes this malformed input through the elasticsearch plugin with local errorfile logging enabled, the double free condition occurs during the cleanup phase of error handling. This memory management flaw falls under the CWE-415 category of double free vulnerabilities, which are classified as a high-severity issue in the Common Weakness Enumeration catalog due to their potential for system compromise. The vulnerability is particularly concerning because it can be triggered remotely without authentication, making it an attractive target for attackers seeking to disrupt syslog services or potentially escalate privileges.
The operational impact of CVE-2013-4758 extends beyond simple denial of service scenarios, as the double free condition can be leveraged to execute arbitrary code on affected systems. This capability stems from the memory corruption that occurs during the second free operation, which can overwrite critical memory structures or function pointers. When combined with the fact that rsyslog typically runs with elevated privileges to handle system logging operations, successful exploitation could result in complete system compromise. The vulnerability affects organizations that rely on rsyslog for centralized logging and monitoring, particularly those using the elasticsearch plugin for log aggregation and analysis. Attackers can exploit this vulnerability to cause persistent service disruption, potentially leading to loss of critical log data, or to establish persistent backdoors through code execution capabilities.
Mitigation strategies for this vulnerability involve immediate patching of affected rsyslog installations to versions 7.4.2 or later, which contain the necessary memory management fixes. Organizations should also implement network segmentation and access controls to limit exposure of rsyslog services to untrusted networks. Additional defensive measures include monitoring for unusual error handling patterns in syslog operations and implementing intrusion detection systems that can identify potential exploitation attempts. The vulnerability aligns with several ATT&CK techniques including T1499 for network disruption and potentially T1059 for command execution, making it a significant concern for security operations centers. Regular vulnerability assessments and patch management programs should be implemented to prevent similar issues, as this vulnerability demonstrates the importance of thorough memory management testing in logging and monitoring systems. Organizations should also consider implementing alternative logging mechanisms or using hardened logging solutions that provide additional protections against memory corruption vulnerabilities.