CVE-2011-1507 in Asterisk
Summary
by MITRE
Asterisk Open Source 1.4.x before 1.4.40.1, 1.6.1.x before 1.6.1.25, 1.6.2.x before 1.6.2.17.3, and 1.8.x before 1.8.3.3 and Asterisk Business Edition C.x.x before C.3.6.4 do not restrict the number of unauthenticated sessions to certain interfaces, which allows remote attackers to cause a denial of service (file descriptor exhaustion and disk space exhaustion) via a series of TCP connections.
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Analysis
by VulDB Data Team • 08/04/2024
The vulnerability identified as CVE-2011-1507 affects Asterisk Open Source and Business Edition installations across multiple version ranges, representing a critical denial of service weakness that exploits the lack of session limiting mechanisms. This issue specifically targets certain interfaces within the Asterisk telephony platform that fail to enforce restrictions on unauthenticated connections, creating a pathway for remote attackers to consume system resources through excessive TCP connection attempts. The vulnerability falls under the category of insufficient resource management as classified by CWE-400, where the system fails to properly control resource allocation and usage limits. The affected versions include Asterisk 1.4.x before 1.4.40.1, 1.6.1.x before 1.6.1.25, 1.6.2.x before 1.6.2.17.3, 1.8.x before 1.8.3.3, and Business Edition C.x.x before C.3.6.4, indicating a widespread impact across multiple release branches that were commonly deployed in enterprise telephony environments.
The technical flaw manifests through the absence of connection rate limiting and session control mechanisms that would normally restrict the number of concurrent unauthenticated connections to sensitive interfaces. When attackers exploit this weakness, they can establish numerous TCP connections to the target Asterisk system without proper authentication, leading to rapid exhaustion of available file descriptors and disk space resources. Each connection consumes system resources including file handles, memory allocations, and disk space for logging and temporary storage. This resource exhaustion ultimately results in the system becoming unresponsive and unable to serve legitimate users or accept new connections. The attack vector is particularly effective because it requires minimal privileges and can be executed remotely, making it an attractive target for malicious actors seeking to disrupt telephony services. The vulnerability directly maps to ATT&CK technique T1499.004 for resource exhaustion attacks, where adversaries consume system resources to prevent legitimate use of services.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire telephony infrastructure deployments. Organizations relying on Asterisk for voice communication services face significant business continuity risks when this vulnerability is exploited, as the denial of service can interrupt critical phone systems, emergency services, and enterprise communication channels. The resource exhaustion affects multiple system components simultaneously, with file descriptor limits being reached first, followed by disk space exhaustion that can cause additional system instability. Network administrators may observe degraded performance, connection timeouts, and complete service outages across the affected telephony systems. The vulnerability particularly impacts organizations using Asterisk for business communications, PBX systems, and VoIP infrastructure, where maintaining continuous service availability is crucial for operational effectiveness and customer satisfaction.
Mitigation strategies for CVE-2011-1507 require immediate implementation of connection limiting measures and system hardening practices. Organizations should upgrade to patched versions of Asterisk as soon as possible, specifically versions 1.4.40.1, 1.6.1.25, 1.6.2.17.3, 1.8.3.3, and Business Edition C.3.6.4 or later. Network-level protections including firewall rules and connection rate limiting should be implemented to restrict the number of incoming connections from any single IP address. System administrators should configure proper resource limits and monitoring for file descriptor usage and disk space consumption. Additional protective measures include implementing authentication requirements for sensitive interfaces, configuring connection timeouts, and establishing automated alerts for unusual connection patterns. The remediation process should also include reviewing and testing the configuration changes to ensure they do not inadvertently disrupt legitimate telephony operations while effectively mitigating the attack vector. Organizations should conduct comprehensive vulnerability assessments to identify any other systems running affected Asterisk versions and prioritize their patching efforts accordingly.