CVE-2014-3634 in rsyslog
Summary
by MITRE
rsyslog before 7.6.6 and 8.x before 8.4.1 and sysklogd 1.5 and earlier allows remote attackers to cause a denial of service (crash), possibly execute arbitrary code, or have other unspecified impact via a crafted priority (PRI) value that triggers an out-of-bounds array access.
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Analysis
by VulDB Data Team • 02/21/2022
The vulnerability identified as CVE-2014-3634 represents a critical security flaw affecting rsyslog versions prior to 7.6.6 and 8.x versions prior to 8.4.1, along with sysklogd versions 1.5 and earlier. This issue stems from improper input validation within the syslog processing pipeline where the system fails to adequately sanitize priority (PRI) values received from remote sources. The flaw manifests when a malicious actor crafts a specially formatted PRI value that exploits a buffer overflow condition, leading to unpredictable system behavior and potential compromise of the affected system.
The technical implementation of this vulnerability resides in the way these logging daemons parse and process syslog messages. When a PRI value is received, the system attempts to map this value to an internal array index for processing. However, the validation mechanism fails to properly check the bounds of this value, allowing an attacker to specify a PRI value that exceeds the allocated array boundaries. This out-of-bounds array access creates a condition where memory corruption occurs, potentially leading to program termination, arbitrary code execution, or other unspecified impacts that can compromise system integrity. The vulnerability aligns with CWE-129, which specifically addresses insufficient validation of length of inputs, and CWE-787, which covers out-of-bounds write operations.
From an operational perspective, this vulnerability presents significant risk to network infrastructure and security monitoring systems that rely on these logging utilities. Attackers can leverage this flaw to perform denial of service attacks against syslog servers, effectively disrupting log collection and system monitoring capabilities. The potential for arbitrary code execution adds another dimension of risk, as successful exploitation could allow attackers to gain unauthorized access to the affected systems. The impact extends beyond simple service disruption, as compromised logging systems can undermine the organization's ability to detect and respond to security incidents. This vulnerability particularly affects systems that receive untrusted syslog data from remote sources, making it a critical concern for network security operations centers and enterprise environments that depend on centralized logging solutions.
Organizations should implement immediate mitigations including updating to patched versions of rsyslog and sysklogd, with the specific recommended versions being rsyslog 7.6.6 and 8.4.1 respectively, or sysklogd 1.5.1 and later. Network segmentation and access controls should be enforced to limit which systems can send syslog data to critical logging servers, reducing the attack surface. Additionally, implementing monitoring solutions that can detect anomalous PRI value patterns and establishing robust incident response procedures are recommended defensive measures. The vulnerability demonstrates the importance of input validation and bounds checking in security-critical applications, reinforcing principles from the ATT&CK framework related to privilege escalation and defense evasion techniques that could be leveraged through such vulnerabilities.