CVE-2018-7286 in Asterisk
Summary
by MITRE
An issue was discovered in Asterisk through 13.19.1, 14.x through 14.7.5, and 15.x through 15.2.1, and Certified Asterisk through 13.18-cert2. res_pjsip allows remote authenticated users to crash Asterisk (segmentation fault) by sending a number of SIP INVITE messages on a TCP or TLS connection and then suddenly closing the connection.
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Analysis
by VulDB Data Team • 11/25/2024
The vulnerability identified as CVE-2018-7286 represents a critical denial-of-service flaw affecting the Asterisk telephony platform across multiple version ranges including 13.19.1 and earlier, 14.7.5 and earlier, 15.2.1 and earlier, and Certified Asterisk 13.18-cert2 and earlier. This vulnerability specifically impacts the res_pjsip module which handles SIP protocol operations, making it a significant concern for organizations relying on Asterisk for voice communication infrastructure. The issue manifests when remote authenticated users exploit a flaw in how the system processes SIP INVITE messages over TCP or TLS connections, leading to system crashes that can disrupt critical communication services.
The technical mechanism behind this vulnerability involves a specific interaction pattern within the SIP processing pipeline where legitimate authenticated users can trigger a segmentation fault by sending multiple SIP INVITE messages followed by abrupt connection termination. This behavior exploits memory management issues in the res_pjsip module where the system fails to properly handle connection state transitions when the TCP or TLS connection is closed immediately after message transmission. The flaw essentially creates a race condition or improper state handling scenario where the application attempts to access freed memory or corrupted data structures, resulting in the segmentation fault that crashes the Asterisk process. This type of vulnerability falls under CWE-121 which describes heap-based buffer overflow conditions, though the specific manifestation here involves memory corruption through improper connection handling rather than direct buffer manipulation.
The operational impact of CVE-2018-7286 extends beyond simple service disruption as it represents a remote authenticated denial-of-service attack that can be executed by users who already possess valid credentials to the system. This makes the vulnerability particularly dangerous in environments where multiple users have legitimate access to the telephony system, as any compromised account could potentially be used to execute this attack. Organizations using Asterisk for mission-critical communications face significant risk of service interruptions that could affect emergency services, business communications, or customer support operations. The vulnerability's exploitation does not require special privileges beyond authentication, making it accessible to attackers who can gain any level of legitimate access to the system, and the attack can be executed repeatedly to maintain the denial-of-service condition.
Mitigation strategies for this vulnerability should focus on immediate patch application as the primary defense mechanism, with the affected versions receiving security updates that address the memory handling issues in the res_pjsip module. Organizations should also implement network-level controls including connection rate limiting and monitoring for unusual patterns of SIP INVITE message sequences followed by connection closures. The implementation of intrusion detection systems that can identify and alert on suspicious SIP traffic patterns provides an additional layer of defense. Security configurations should include limiting the number of concurrent connections and implementing proper connection timeout mechanisms to reduce the window of opportunity for exploitation. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique for network denial-of-service attacks, and organizations should consider implementing network segmentation to limit the impact of such attacks. Additionally, regular security assessments of telephony infrastructure and maintaining up-to-date security patches for all components, including third-party modules like res_pjsip, are essential practices to prevent exploitation of similar vulnerabilities in the future.