CVE-2013-2264 in Asterisk
Summary
by MITRE
The SIP channel driver in Asterisk Open Source 1.8.x before 1.8.20.2, 10.x before 10.12.2, and 11.x before 11.2.2; Certified Asterisk 1.8.15 before 1.8.15-cert2; Asterisk Business Edition (BE) C.3.x before C.3.8.1; and Asterisk Digiumphones 10.x-digiumphones before 10.12.2-digiumphones exhibits different behavior for invalid INVITE, SUBSCRIBE, and REGISTER transactions depending on whether the user account exists, which allows remote attackers to enumerate account names by (1) reading HTTP status codes, (2) reading additional text in a 403 (aka Forbidden) response, or (3) observing whether certain retransmissions occur.
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Analysis
by VulDB Data Team • 05/06/2021
The vulnerability described in CVE-2013-2264 represents a critical information disclosure flaw within the Session Initiation Protocol (SIP) channel driver of various Asterisk versions. This issue affects multiple release branches including 1.8.x, 10.x, and 11.x versions of the open source Asterisk platform, as well as certified and business editions from Digium. The core problem lies in the inconsistent handling of invalid SIP transactions across different user account states, creating a scenario where attackers can systematically determine which user accounts exist within the system through careful observation of server responses. This vulnerability directly maps to CWE-200, which encompasses information exposure through improper error handling, and aligns with ATT&CK technique T1212, which involves exploitation of information disclosure vulnerabilities to gather system intelligence.
The technical implementation of this vulnerability stems from the SIP channel driver's differential response behavior when processing invalid INVITE, SUBSCRIBE, and REGISTER requests. When an attacker sends malformed SIP requests to the server, the system responds differently based on whether the target user account exists in the configuration. For existing accounts, the server typically returns a 403 Forbidden response with additional descriptive text indicating account validation failures, while non-existent accounts may generate different status codes or response patterns. This inconsistency in response handling creates a side-channel attack vector that allows adversaries to enumerate valid user accounts through simple HTTP status code analysis or by observing response timing characteristics such as retransmission patterns.
The operational impact of this vulnerability extends beyond simple account enumeration, as it provides attackers with foundational intelligence for subsequent attacks. Once valid account names are discovered, attackers can proceed with more sophisticated attacks including password spraying, brute force attempts, or credential stuffing attacks against the enumerated accounts. The vulnerability affects organizations using Asterisk for voice over IP communications, potentially compromising telephony infrastructure and leading to unauthorized access to voice services, call interception, or even complete system compromise if additional vulnerabilities exist. This flaw particularly impacts businesses relying on Asterisk for their communication infrastructure, as it undermines fundamental security assumptions about account privacy and access control.
Mitigation strategies for CVE-2013-2264 involve immediate patching of affected Asterisk versions to the recommended secure releases including 1.8.20.2, 10.12.2, and 11.2.2 for their respective branches. Organizations should also implement rate limiting and connection throttling mechanisms to prevent rapid enumeration attempts, while ensuring that all SIP responses provide consistent error handling regardless of account existence. Network-level protections such as firewall rules and intrusion detection systems can help detect and block suspicious SIP traffic patterns. Additionally, administrators should conduct comprehensive security assessments of their telephony infrastructure, review SIP configuration settings, and implement proper logging and monitoring to detect potential exploitation attempts. The vulnerability demonstrates the importance of consistent error handling in security-critical systems and serves as a reminder of the need for thorough security testing of communication protocols in enterprise environments.