CVE-2012-5976 in Asterisk
Summary
by MITRE
Multiple stack consumption vulnerabilities in Asterisk Open Source 1.8.x before 1.8.19.1, 10.x before 10.11.1, and 11.x before 11.1.2; Certified Asterisk 1.8.11 before 1.8.11-cert10; and Asterisk Digiumphones 10.x-digiumphones before 10.11.1-digiumphones allow remote attackers to cause a denial of service (daemon crash) via TCP data using the (1) SIP, (2) HTTP, or (3) XMPP protocol.
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Analysis
by VulDB Data Team • 07/20/2017
The vulnerability identified as CVE-2012-5976 represents a critical stack consumption issue affecting multiple versions of Asterisk Open Source and Certified Asterisk implementations. This vulnerability specifically targets the SIP, HTTP, and XMPP protocols within the Asterisk telephony platform, creating a remote denial of service condition that can crash the daemon and disrupt critical communication services. The flaw stems from inadequate input validation and memory management practices within the protocol handling components, allowing malicious actors to exploit the system through carefully crafted TCP data packets.
The technical implementation of this vulnerability involves the exploitation of stack memory consumption patterns during protocol processing. When Asterisk receives malformed TCP data through any of the three affected protocols, the system's stack memory consumption grows uncontrollably due to improper buffer handling and recursive processing of malicious input. This leads to stack overflow conditions that cause the Asterisk daemon to terminate unexpectedly, resulting in complete service disruption for all connected telephony systems. The vulnerability is particularly dangerous because it affects core communication protocols that are fundamental to VoIP infrastructure, making it an attractive target for attackers seeking to disrupt business communications.
From an operational impact perspective, this vulnerability poses severe risks to organizations relying on Asterisk-based telephony systems. The remote exploitation capability means that attackers can trigger denial of service conditions from external networks without requiring authentication or physical access to the system. This creates a significant threat to business continuity and communication infrastructure, particularly affecting enterprises, service providers, and organizations with critical communication requirements. The vulnerability affects a broad range of Asterisk versions including 1.8.x through 1.8.19.0, 10.x through 10.11.0, and 11.x through 11.1.1, indicating a widespread impact across multiple release lines and certification levels.
The vulnerability aligns with CWE-121 Stack-based Buffer Overflow, which describes the classic condition where data written to a stack buffer exceeds the buffer's capacity, potentially corrupting adjacent memory locations. Additionally, this issue maps to ATT&CK technique T1499.004 for Network Denial of Service, as it enables attackers to consume system resources and cause service disruption. The attack surface is particularly concerning given that SIP, HTTP, and XMPP are commonly exposed protocols in telephony environments, often running on standard ports and accessible from external networks without proper network segmentation. Organizations implementing Asterisk systems without proper input validation and resource limiting measures are particularly vulnerable to exploitation.
Mitigation strategies should focus on immediate patching of affected versions to the recommended secure releases including Asterisk 1.8.19.1, 10.11.1, and 11.1.2, along with the corresponding Certified Asterisk and Digiumphones versions. Network segmentation and firewall rules should be implemented to restrict access to SIP, HTTP, and XMPP ports to trusted networks only, while implementing rate limiting and connection tracking mechanisms to prevent exploitation attempts. Additionally, monitoring systems should be deployed to detect unusual stack memory consumption patterns and abnormal daemon behavior, providing early warning capabilities for potential exploitation attempts. Regular security assessments and vulnerability scanning of telephony infrastructure should be conducted to identify and remediate similar issues before they can be exploited by malicious actors.