CVE-2018-8828 in Kamailio
Summary
by MITRE
A Buffer Overflow issue was discovered in Kamailio before 4.4.7, 5.0.x before 5.0.6, and 5.1.x before 5.1.2. A specially crafted REGISTER message with a malformed branch or From tag triggers an off-by-one heap-based buffer overflow in the tmx_check_pretran function in modules/tmx/tmx_pretran.c.
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Analysis
by VulDB Data Team • 02/22/2023
The vulnerability identified as CVE-2018-8828 represents a critical buffer overflow flaw within the Kamailio SIP server software, affecting multiple version ranges including 4.4.6 and earlier, 5.0.5 and earlier, and 5.1.1 and earlier. This issue resides in the transaction management module of Kamailio, specifically within the tmx_check_pretran function located in modules/tmx/tmx_pretran.c. The vulnerability manifests when processing specially crafted REGISTER messages that contain malformed branch or From tags, creating a condition where memory corruption occurs during the processing of SIP signaling traffic.
The technical exploitation of this vulnerability occurs through a heap-based buffer overflow that results from an off-by-one error in memory allocation handling. When Kamailio receives a REGISTER message with malformed branch or From tags, the tmx_check_pretran function fails to properly validate the length of these tags before attempting to copy them into fixed-size buffers. This improper boundary checking allows an attacker to write data beyond the allocated buffer boundaries, potentially leading to memory corruption that can be leveraged for arbitrary code execution or service disruption. The flaw operates at the application layer and specifically targets the SIP transaction handling mechanism that is fundamental to VoIP communications.
The operational impact of this vulnerability extends beyond simple service interruption to potentially enable remote code execution on affected systems. Attackers can exploit this flaw by sending malicious REGISTER messages to Kamailio servers, which could result in system crashes, denial of service conditions, or more severe consequences including complete system compromise. Given that Kamailio is widely deployed as a SIP server in telecommunications infrastructure, enterprise communications systems, and VoIP services, the potential attack surface is extensive. The vulnerability affects systems that rely on Kamailio for handling SIP registration traffic, making it particularly dangerous in environments where SIP servers are exposed to untrusted networks or external communication channels.
Mitigation strategies for CVE-2018-8828 primarily focus on immediate software updates to patched versions of Kamailio, specifically versions 4.4.7, 5.0.6, and 5.1.2 or later. Organizations should prioritize patch management and ensure all instances of Kamailio are updated to prevent exploitation. Network-level protections can include implementing SIP message filtering and validation mechanisms to detect and block malformed REGISTER messages before they reach the vulnerable software components. Additionally, deploying intrusion detection systems that monitor for suspicious SIP traffic patterns and implementing proper access controls to limit exposure of Kamailio servers to untrusted networks can provide additional defense layers. This vulnerability aligns with CWE-121, heap-based buffer overflow, and represents a technique that could be categorized under ATT&CK tactic TA0043, exploitation for execution, and technique T1203, exploitation for privilege escalation, when properly leveraged by attackers.
The vulnerability demonstrates the critical importance of proper input validation in network protocols and highlights the potential for seemingly minor flaws in transaction handling to result in severe security consequences. Given the widespread adoption of Kamailio in VoIP infrastructure, this vulnerability underscores the necessity for robust security practices in telecommunications software development and deployment, emphasizing the need for regular security assessments and prompt patch deployment across all network infrastructure components.