CVE-2018-16657 in Kamailio
Summary
by MITRE
In Kamailio before 5.0.7 and 5.1.x before 5.1.4, a crafted SIP message with an invalid Via header causes a segmentation fault and crashes Kamailio. The reason is missing input validation in the crcitt_string_array core function for calculating a CRC hash for To tags. (An additional error is present in the check_via_address core function: this function also misses input validation.) This could result in denial of service and potentially the execution of arbitrary code.
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Analysis
by VulDB Data Team • 05/07/2023
The vulnerability CVE-2018-16657 represents a critical denial of service weakness in Kamailio SIP server software affecting versions prior to 5.0.7 and 5.1.x before 5.1.4. This flaw manifests when processing crafted SIP messages containing invalid Via headers that trigger segmentation faults and subsequent application crashes. The root cause lies in insufficient input validation within the crcitt_string_array core function responsible for calculating CRC hashes used in To tag generation. The vulnerability operates at the core networking layer where SIP protocol parsing occurs, making it particularly dangerous as it can be exploited through legitimate network traffic without requiring special privileges or authentication. The flaw specifically targets the cryptographic checksum calculation mechanism that Kamailio employs for maintaining session state and tracking SIP transactions, creating a pathway for malicious actors to disrupt service availability. This vulnerability directly maps to CWE-121 which describes heap-based buffer overflow conditions, and also aligns with ATT&CK technique T1499.100 which covers network denial of service attacks.
The technical implementation of this vulnerability exploits the absence of proper validation in two critical functions within Kamailio's core processing pipeline. The crcitt_string_array function fails to validate input parameters before performing hash calculations, allowing malformed Via header data to cause memory corruption during CRC processing. Additionally, the check_via_address function contains identical validation gaps, creating multiple entry points for exploitation. When these functions process malformed input, they attempt to access memory locations beyond allocated buffers or manipulate pointers incorrectly, resulting in segmentation faults that crash the entire Kamailio process. The attack vector requires sending a specially crafted SIP message containing an invalid Via header field, which can be constructed using standard SIP protocol structures but with malformed parameters that bypass normal parsing validation. This allows attackers to trigger the vulnerable code path without requiring elevated privileges or specific authentication credentials.
The operational impact of CVE-2018-16657 extends beyond simple service disruption to potentially enabling more sophisticated attack scenarios. While the primary effect is denial of service through application crashes, the underlying memory corruption vulnerability creates opportunities for arbitrary code execution under certain conditions. Network administrators face significant challenges in detecting and mitigating this vulnerability since it can be triggered by legitimate-looking SIP traffic that appears normal to standard network monitoring tools. The vulnerability affects Kamailio's core functionality as a SIP proxy and registrar, meaning that any service relying on these capabilities becomes vulnerable to disruption. Organizations using Kamailio for voice over IP services, session border control, or SIP-based communication infrastructure face substantial risk of service outages that could impact business continuity and customer satisfaction. The vulnerability's exploitation is particularly concerning because it can be performed remotely without authentication, making it accessible to any network entity capable of sending SIP messages to the target system.
Mitigation strategies for CVE-2018-16657 should prioritize immediate software updates to versions 5.0.7 or 5.1.4 and later, which contain the necessary input validation patches. Network administrators should implement strict SIP message filtering rules that validate Via header format and content before allowing messages to reach the Kamailio processing engine. Additional defensive measures include deploying intrusion detection systems capable of identifying suspicious SIP traffic patterns and implementing rate limiting to prevent exploitation through flood attacks. Organizations should also consider implementing redundant SIP infrastructure and failover mechanisms to minimize impact from potential exploitation attempts. The vulnerability's classification as a memory corruption issue suggests that additional runtime protections such as address space layout randomization and stack canaries may provide supplementary defense in depth. Regular security assessments of SIP infrastructure components and monitoring for unusual application crash patterns should be implemented as part of ongoing security operations. System administrators must also ensure that all network devices and services that interact with Kamailio are updated to prevent exploitation through relayed or forwarded SIP traffic. The remediation process should include thorough testing of updated configurations to ensure that legitimate SIP traffic continues to function properly while the vulnerability is eliminated.