CVE-2017-16671 in Asterisk
Summary
by MITRE
A Buffer Overflow issue was discovered in Asterisk Open Source 13 before 13.18.1, 14 before 14.7.1, and 15 before 15.1.1 and Certified Asterisk 13.13 before 13.13-cert7. No size checking is done when setting the user field for Party B on a CDR. Thus, it is possible for someone to use an arbitrarily large string and write past the end of the user field storage buffer. NOTE: this is different from CVE-2017-7617, which was only about the Party A buffer.
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Analysis
by VulDB Data Team • 01/23/2021
The vulnerability identified as CVE-2017-16671 represents a critical buffer overflow flaw within the Asterisk Open Source telephony platform that affects multiple version ranges including 13 before 13.18.1, 14 before 14.7.1, 15 before 15.1.1, and Certified Asterisk 13.13 before 13.13-cert7. This security weakness specifically targets the Call Detail Record (CDR) functionality where no size validation occurs when processing the user field for Party B, creating a pathway for malicious actors to exploit the system through carefully crafted input sequences. The flaw is categorized under CWE-121 as a stack-based buffer overflow, which occurs when a program writes data beyond the boundaries of a fixed-length buffer, potentially leading to memory corruption and arbitrary code execution.
The technical implementation of this vulnerability stems from inadequate input validation within the CDR processing subsystem where the system accepts user-provided data for Party B without enforcing size limits on the input buffer. When an attacker submits an excessively large string through the user field parameter, the system fails to check whether the data exceeds the allocated buffer space, allowing the overflow to occur and overwrite adjacent memory locations. This particular variant differs from CVE-2017-7617 which addressed similar issues in Party A fields, making CVE-2017-16671 a distinct but related vulnerability affecting the broader CDR framework. The attack surface is particularly concerning as CDR generation occurs during normal telephony operations, meaning that exploitation could happen through legitimate call processing activities without requiring special privileges or authentication.
From an operational perspective, this vulnerability poses significant risks to organizations relying on Asterisk for voice communication infrastructure, as it can be exploited remotely through crafted SIP or other telephony protocol messages. The impact extends beyond simple system instability to potentially enable full system compromise, as buffer overflows in telephony applications can be leveraged for privilege escalation and persistent access. The vulnerability aligns with ATT&CK technique T1059.007 for command and script injection, where attackers could potentially execute arbitrary code through the overflowed memory regions. Organizations using Asterisk in production environments face potential data breaches, service disruption, and unauthorized access to their telephony infrastructure, particularly in scenarios where the system is exposed to untrusted networks or external call sources.
Mitigation strategies for CVE-2017-16671 primarily involve immediate deployment of patched versions from the Asterisk project, specifically upgrading to versions 13.18.1, 14.7.1, 15.1.1, or the corresponding certified releases. Network segmentation and firewall rules should be implemented to restrict access to telephony services, limiting exposure to potential attackers. Input validation should be enhanced at all levels of the application stack, with additional monitoring and logging of CDR generation activities to detect anomalous patterns. System administrators should conduct thorough security assessments of their telephony infrastructure, including reviewing call routing configurations and implementing intrusion detection systems to monitor for exploitation attempts. The vulnerability also highlights the importance of proper software security practices including input sanitization, buffer size validation, and regular security updates as recommended by NIST guidelines for secure software development lifecycle practices.