CVE-2016-6271 in Bzrtp Library
Summary
by MITRE
The Bzrtp library (aka libbzrtp) 1.0.x before 1.0.4 allows man-in-the-middle attackers to conduct spoofing attacks by leveraging a missing HVI check on DHPart2 packet reception.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2016-6271 affects the Bzrtp library version 1.0.x prior to 1.0.4, representing a critical security flaw that undermines the integrity of encrypted communications. This library serves as a cryptographic implementation for the ZRTP protocol, which is widely used in voice over IP applications to establish secure peer-to-peer connections. The flaw resides in the library's handling of Diffie-Hellman key exchange messages, specifically during the reception of DHPart2 packets that are crucial for establishing shared secrets between communicating parties. The vulnerability creates a pathway for attackers to manipulate the cryptographic handshake process without detection, fundamentally compromising the security assurances that ZRTP is designed to provide.
The technical root cause of this vulnerability stems from the absence of a critical HVI (Hash Value Integrity) check during the processing of DHPart2 packets within the Bzrtp library implementation. When a malicious actor intercepts and modifies the DHPart2 message during transmission, the library fails to validate the integrity of the received data against expected cryptographic hashes. This omission allows an attacker to inject modified parameters into the key exchange process, potentially enabling them to establish separate cryptographic sessions with each party in a communication, effectively creating a man-in-the-middle position. The missing validation mechanism violates fundamental cryptographic principles that require message integrity verification to prevent tampering during transmission.
The operational impact of this vulnerability extends beyond simple security compromise, as it fundamentally undermines trust in the encrypted communication channel. An attacker exploiting this flaw can successfully impersonate legitimate participants in VoIP conversations, potentially gaining access to sensitive information or disrupting communication services entirely. The vulnerability affects any system utilizing the affected version of libbzrtp, including but not limited to enterprise communication systems, VoIP phones, and unified communications platforms. The implications are particularly severe in environments where confidentiality and authentication are paramount, such as financial institutions, healthcare organizations, and government agencies that rely on secure voice communications.
Security professionals should consider this vulnerability in the context of the broader ATT&CK framework, where it maps to techniques involving credential access through protocol manipulation and network infiltration. The vulnerability aligns with CWE-310, which addresses cryptographic weaknesses, specifically focusing on missing cryptographic checks or validation mechanisms. Organizations should implement immediate mitigations including updating to libbzrtp version 1.0.4 or later, which includes the necessary HVI validation checks. Additionally, network monitoring solutions should be enhanced to detect anomalous key exchange patterns that might indicate exploitation attempts. The remediation process should also include comprehensive security assessments of all systems utilizing this library to ensure complete elimination of the vulnerability across the organization's communication infrastructure.