CVE-2018-12228 in Open Source
Summary
by MITRE
An issue was discovered in Asterisk Open Source 15.x before 15.4.1. When connected to Asterisk via TCP/TLS, if the client abruptly disconnects, or sends a specially crafted message, then Asterisk gets caught in an infinite loop while trying to read the data stream. This renders the system unusable.
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Analysis
by VulDB Data Team • 08/15/2024
The vulnerability identified as CVE-2018-12228 represents a critical denial of service flaw within Asterisk Open Source versions 15.x prior to 15.4.1. This issue specifically affects the telephony infrastructure component that handles TCP/TLS connections, creating a scenario where legitimate system operations become impossible due to resource exhaustion. The flaw manifests when Asterisk encounters unexpected client disconnections or malformed data streams during active communication sessions, leading to system instability and complete service unavailability.
The technical root cause of this vulnerability stems from inadequate input validation and error handling mechanisms within Asterisk's protocol processing layer. When a client establishes a TCP/TLS connection to the Asterisk server and subsequently either disconnects abruptly or transmits malformed messages, the system fails to properly terminate the data reading loop. This condition creates a state where Asterisk continuously attempts to process incoming data from the corrupted connection stream, resulting in an infinite loop that consumes excessive CPU resources and prevents the system from handling legitimate incoming requests. The flaw operates at the application layer and specifically targets the SIP protocol implementation within Asterisk's communication stack.
From an operational perspective, this vulnerability presents a severe risk to telephony services that depend on Asterisk for voice communication infrastructure. The infinite loop condition causes the system to become completely unresponsive, effectively rendering all voice services unavailable to legitimate users. Network administrators face the challenge of maintaining service availability when attackers can exploit this flaw to disrupt critical communication systems. The impact extends beyond simple service interruption as the resource exhaustion can potentially affect system stability, leading to crashes or requiring manual intervention to restore normal operations.
This vulnerability aligns with CWE-835, which addresses infinite loops in software applications, and maps to ATT&CK technique T1499.004, which covers network disruption through resource exhaustion attacks. The flaw demonstrates poor defensive programming practices where the system does not implement proper timeout mechanisms or connection state management. Organizations should implement immediate mitigations including upgrading to Asterisk 15.4.1 or later versions, implementing connection rate limiting, and deploying network-level protections to prevent exploitation. Additionally, regular monitoring of system resource utilization and connection states can help detect early signs of exploitation attempts, while maintaining current security patches ensures protection against similar vulnerabilities in the future.