CVE-2011-1175 in Asterisk
Summary
by MITRE
tcptls.c in the TCP/TLS server in Asterisk Open Source 1.6.1.x before 1.6.1.23, 1.6.2.x before 1.6.2.17.1, and 1.8.x before 1.8.3.1 allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) by establishing many short TCP sessions to services that use a certain TLS API.
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Analysis
by VulDB Data Team • 10/21/2021
The vulnerability described in CVE-2011-1175 represents a critical denial of service weakness within the Asterisk Open Source telephony platform, specifically affecting versions prior to the mentioned patch releases. This flaw exists in the tcptls.c component of the TCP/TLS server implementation, which is responsible for managing secure communication channels for various telephony services. The vulnerability manifests when remote attackers exploit a NULL pointer dereference condition that occurs during the handling of multiple short-lived TCP sessions, ultimately leading to daemon crashes and complete service disruption.
The technical root cause of this vulnerability stems from inadequate input validation and error handling within the TLS session management code. When numerous brief TCP connections are established to services utilizing the affected TLS API, the system fails to properly validate pointer references during session termination or cleanup phases. This NULL pointer dereference condition creates a scenario where the application attempts to access memory locations that have not been properly initialized or allocated, resulting in immediate process termination and system instability. The vulnerability is particularly insidious because it can be triggered through relatively simple network operations without requiring authentication or specialized privileges.
The operational impact of CVE-2011-1175 extends beyond simple service disruption to potentially compromise entire telephony infrastructure reliability. Organizations relying on Asterisk for critical communications services face significant risk of unplanned outages that could affect business operations, emergency services, or customer communications. The vulnerability's exploitation requires minimal resources and can be executed by any remote attacker with network access to the affected system, making it a particularly attractive target for malicious actors seeking to disrupt services. This weakness directly violates security principles outlined in CWE-476, which addresses NULL pointer dereference conditions, and aligns with ATT&CK technique T1499.004 for network denial of service attacks.
Mitigation strategies for this vulnerability require immediate patch application to affected Asterisk versions, with administrators prioritizing updates to versions 1.6.1.23, 1.6.2.17.1, or 1.8.3.1 and later. Network administrators should implement rate limiting and connection throttling mechanisms to prevent exploitation through excessive connection attempts, while also monitoring for unusual patterns of TCP session establishment. Additionally, organizations should consider implementing intrusion detection systems capable of identifying the specific attack patterns associated with this vulnerability, and establish incident response procedures to quickly address any exploitation attempts. The vulnerability's classification under CWE-476 emphasizes the need for robust pointer validation and error handling practices in all network service implementations, while the ATT&CK framework's categorization highlights the importance of network-level protections against such denial of service vectors.