CVE-2014-4048 in Asterisk
Summary
by MITRE
The PJSIP Channel Driver in Asterisk Open Source before 12.3.1 allows remote attackers to cause a denial of service (deadlock) by terminating a subscription request before it is complete, which triggers a SIP transaction timeout.
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Analysis
by VulDB Data Team • 06/22/2021
The vulnerability identified as CVE-2014-4048 affects the PJSIP Channel Driver within Asterisk Open Source versions prior to 12.3.1, presenting a significant denial of service risk that can be exploited remotely by malicious actors. This flaw specifically targets the handling of SIP subscription requests within the Asterisk telephony platform, which is widely deployed in enterprise communications systems and VoIP infrastructure. The vulnerability resides in how the system manages SIP transactions when subscription requests are prematurely terminated, creating a condition that leads to system deadlock and complete service disruption.
The technical mechanism behind this vulnerability involves the improper handling of SIP transaction states within the PJSIP channel driver architecture. When a remote attacker sends a subscription request to the Asterisk server and then abruptly terminates the connection before the subscription process completes, the system enters a deadlock state. This occurs because the underlying SIP transaction management code fails to properly clean up or handle the incomplete transaction state, resulting in a thread or process becoming permanently blocked. The system attempts to manage the SIP transaction timeout mechanism, but the premature termination creates a race condition or state management flaw that prevents proper resource cleanup and leads to the complete blocking of the affected service thread.
From an operational perspective, this vulnerability poses a severe threat to organizations relying on Asterisk for their communication infrastructure, as it can be exploited without requiring authentication or specialized privileges. Attackers can simply establish a subscription request and then disconnect before completion, causing the targeted Asterisk server to become unresponsive and unable to process additional SIP requests. This type of denial of service attack can result in complete communication outages for businesses, potentially affecting customer service operations, emergency communication systems, and critical business processes that depend on VoIP infrastructure. The impact extends beyond simple service disruption to potentially compromising business continuity and operational reliability.
The vulnerability aligns with CWE-667, which addresses improper lock handling in concurrent programming, and relates to the broader category of resource management flaws that can lead to system instability. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, specifically targeting the availability of services through denial of service attacks, and represents a common attack pattern that leverages protocol implementation weaknesses. Organizations should implement immediate mitigations including upgrading to Asterisk version 12.3.1 or later, which contains the necessary patches to properly handle subscription request termination scenarios. Additional protective measures include implementing network-level access controls to limit SIP traffic exposure, configuring proper timeout values for subscription requests, and monitoring for unusual patterns of subscription terminations that might indicate attempted exploitation of this vulnerability.