CVE-2012-3812 in Asterisk
Summary
by MITRE
Double free vulnerability in apps/app_voicemail.c in Asterisk Open Source 1.8.x before 1.8.13.1 and 10.x before 10.5.2, Certified Asterisk 1.8.11-certx before 1.8.11-cert4, and Asterisk Digiumphones 10.x.x-digiumphones before 10.5.2-digiumphones allows remote authenticated users to cause a denial of service (daemon crash) by establishing multiple voicemail sessions and accessing both the Urgent mailbox and the INBOX mailbox.
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Analysis
by VulDB Data Team • 12/05/2021
The CVE-2012-3812 vulnerability represents a critical double free error in the Asterisk voicemail application module that affects multiple versions of the open source telephony platform. This vulnerability resides in the apps/app_voicemail.c file and manifests when authenticated remote attackers exploit specific conditions during voicemail session handling. The flaw specifically occurs when a user establishes multiple voicemail sessions and simultaneously accesses both the Urgent mailbox and the INBOX mailbox, creating a scenario where memory management functions are invoked twice on the same memory block. This type of vulnerability falls under CWE-415, which categorizes improper handling of memory allocation and deallocation operations in software applications.
The technical execution of this vulnerability involves a complex interaction between the voicemail session management and memory deallocation processes within Asterisk's application layer. When an authenticated user accesses both mailbox types concurrently, the application's internal memory management routines encounter a situation where a memory pointer is freed twice, leading to undefined behavior and potential memory corruption. This double free condition can result in heap corruption that ultimately causes the Asterisk daemon to crash and restart, creating a denial of service condition that affects all telephony services dependent on the platform. The vulnerability specifically impacts Asterisk versions 1.8.x prior to 1.8.13.1, 10.x prior to 10.5.2, Certified Asterisk 1.8.11-certx prior to 1.8.11-cert4, and Asterisk Digiumphones 10.x.x-digiumphones prior to 10.5.2-digiumphones, indicating a widespread exposure across multiple release lines of the telephony platform.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on Asterisk for their communication infrastructure, as it allows authenticated attackers to disrupt service availability without requiring privileged access to the system. The attack requires only legitimate user authentication credentials, making it particularly dangerous in environments where multiple users have access to voicemail services. The impact extends beyond simple service disruption, as the daemon crash can result in loss of ongoing calls, missed voicemail notifications, and potential data integrity issues within the voicemail system. This vulnerability aligns with ATT&CK technique T1499.004, which covers the use of denial of service attacks against network services, and represents a critical weakness in the application's memory management that could be exploited as part of broader attack campaigns targeting telephony infrastructure.
Organizations should implement immediate mitigations including applying the vendor patches released for affected versions, which address the double free condition through proper memory management controls and validation of mailbox access operations. Network segmentation and access controls should be strengthened to limit the scope of potential exploitation, while monitoring systems should be deployed to detect anomalous voicemail session patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of thorough memory management testing in telephony applications and highlights the need for proper input validation in multi-user environments where concurrent access to shared resources can create complex race conditions and memory corruption scenarios. Security teams should also consider implementing intrusion detection systems that can identify patterns consistent with this specific attack vector and establish incident response procedures for rapid daemon recovery and service restoration.