CVE-2012-4737 in Asterisk
Summary
by MITRE
channels/chan_iax2.c in Asterisk Open Source 1.8.x before 1.8.15.1 and 10.x before 10.7.1, Certified Asterisk 1.8.11 before 1.8.11-cert7, Asterisk Digiumphones 10.x.x-digiumphones before 10.7.1-digiumphones, and Asterisk Business Edition C.3.x before C.3.7.6 does not enforce ACL rules during certain uses of peer credentials, which allows remote authenticated users to bypass intended outbound-call restrictions by leveraging the availability of these credentials.
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Analysis
by VulDB Data Team • 04/12/2021
The vulnerability identified as CVE-2012-4737 resides within the IAX2 channel driver implementation of Asterisk Open Source and its certified variants, specifically affecting versions prior to the mentioned secure releases. This flaw manifests in the channels/chan_iax2.c component where access control lists fail to properly validate peer credentials during specific outbound call operations. The issue creates a critical security gap that allows authenticated attackers to circumvent intended call restrictions through the exploitation of available peer credentials, effectively undermining the security model designed to control outbound communication flows. The vulnerability specifically impacts the IAX2 protocol implementation which is commonly used for voice over IP communications in telephony systems.
The technical root cause of this vulnerability stems from improper enforcement of access control mechanisms within the IAX2 channel driver during peer credential validation processes. When legitimate users authenticate to the system and establish peer connections, the system should verify that these authenticated peers comply with configured access restrictions before permitting outbound calls. However, the flaw occurs during certain operational scenarios where the system fails to properly cross-reference peer credentials against configured access control lists, allowing attackers to leverage existing valid peer credentials to make unauthorized outbound calls. This represents a classic access control bypass vulnerability where the system's authorization checks are insufficiently enforced during specific operational states.
The operational impact of this vulnerability extends beyond simple unauthorized call access, creating potential for significant security compromise within telephony infrastructure. An authenticated user with legitimate peer credentials could exploit this flaw to make calls outside their intended scope, potentially accessing premium rate numbers, international destinations, or restricted internal systems. This vulnerability particularly affects organizations relying on Asterisk for business telephony where outbound call restrictions are implemented to control costs and prevent unauthorized access to external systems. The ability to bypass these controls could result in financial losses through unauthorized calling, potential data exfiltration through call channels, and disruption of normal business communications. The vulnerability's impact is amplified in environments where IAX2 is the primary communication protocol and where proper network segmentation and access controls are not implemented at multiple layers.
Mitigation strategies for this vulnerability require immediate implementation of the vendor-provided security patches and updates to the affected Asterisk versions. Organizations should ensure all systems are updated to versions 1.8.15.1, 10.7.1, or their respective certified counterparts as specified in the security advisories. Network administrators should also implement additional monitoring and logging of IAX2 communications to detect anomalous call patterns that might indicate exploitation attempts. The configuration of access control lists should be reviewed and strengthened to ensure proper enforcement of call restrictions, and redundant authentication mechanisms should be implemented where possible. Security teams should also consider implementing network segmentation to isolate telephony systems from critical business networks, following the principle of least privilege to minimize the potential impact of credential compromise. This vulnerability aligns with CWE-284 Access Control Bypass and maps to ATT&CK technique T1078 Valid Accounts, where adversaries leverage legitimate credentials to bypass security controls and gain unauthorized access to systems or network resources.