CVE-2014-4045 in Asterisk
Summary
by MITRE
The Publish/Subscribe Framework in the PJSIP channel driver in Asterisk Open Source 12.x before 12.3.1, when sub_min_expiry is set to zero, allows remote attackers to cause a denial of service (assertion failure and crash) via an unsubscribe request when not subscribed to the device.
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Analysis
by VulDB Data Team • 06/22/2021
The vulnerability described in CVE-2014-4045 represents a critical denial of service flaw within the Publish/Subscribe Framework of Asterisk Open Source versions 12.x prior to 12.3.1. This issue specifically affects the PJSIP channel driver implementation where the sub_min_expiry parameter is configured to zero, creating a condition that remote attackers can exploit to trigger system crashes. The vulnerability manifests when an unsubscribe request is processed against a device that was never actually subscribed, leading to an assertion failure that terminates the Asterisk service.
The technical root cause of this vulnerability lies in the improper handling of unsubscribe operations within the PJSIP channel driver's subscription management logic. When sub_min_expiry is set to zero, the framework fails to properly validate subscription states before processing unsubscribe requests, resulting in a condition where an assertion check fails catastrophically. This flaw operates at the protocol level within the SIP channel driver, specifically affecting the publish/subscribe mechanism used for managing device subscriptions and notifications. The vulnerability is classified under CWE-20, representing an improper input validation issue, where the system does not adequately verify the state of subscription objects before performing operations on them. From an operational perspective, this vulnerability represents a significant risk to VoIP infrastructure as it allows remote attackers to disrupt service availability without requiring authentication or privileged access.
The operational impact of CVE-2014-4045 extends beyond simple service disruption, as it can lead to complete system unavailability and potential business continuity issues for organizations relying on Asterisk for their communication infrastructure. Attackers can repeatedly exploit this vulnerability to cause multiple service crashes, creating persistent denial of service conditions that may require manual intervention to restore normal operations. The attack vector is particularly concerning as it requires no authentication and can be executed remotely, making it an attractive target for malicious actors seeking to disrupt communication services. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a classic example of a buffer overflow or assertion failure that can be exploited for service disruption. Organizations utilizing Asterisk 12.x versions prior to 12.3.1 are particularly vulnerable as the fix requires a simple version upgrade, but the window of exposure can be significant for systems that do not maintain current security patches. The vulnerability demonstrates how seemingly minor configuration parameters can create critical security weaknesses in telephony systems, highlighting the importance of proper input validation and state management in real-time communication frameworks.
The mitigation strategy for this vulnerability focuses primarily on upgrading to Asterisk version 12.3.1 or later, which contains the necessary code fixes to properly handle unsubscribe operations when sub_min_expiry is set to zero. Additionally, system administrators should consider implementing network-level protections such as firewall rules that restrict access to SIP signaling ports, although this approach only provides partial protection as the vulnerability can be exploited through legitimate network paths. Organizations should also implement monitoring solutions to detect unusual patterns of service disruptions that might indicate exploitation attempts. The fix implemented in the patched versions addresses the core assertion failure by adding proper state validation checks before processing unsubscribe requests, ensuring that the system does not attempt operations on unsubscribed devices. This vulnerability underscores the importance of maintaining current security patches for telephony infrastructure and demonstrates how protocol-level flaws can have severe operational consequences in mission-critical communication systems.