CVE-2017-16872 in PJSIP
Summary
by MITRE
An issue was discovered in Teluu pjproject (pjlib and pjlib-util) in PJSIP before 2.7.1. Parsing the numeric header fields in a SIP message (like cseq, ttl, port, etc.) all had the potential to overflow, either causing unintended values to be captured or, if the values were subsequently converted back to strings, a buffer overrun. This will lead to a potential exploit using carefully crafted invalid values.
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Analysis
by VulDB Data Team • 01/11/2023
The vulnerability identified as CVE-2017-16872 represents a critical buffer overflow issue within the Teluu pjproject library, specifically affecting pjlib and pjlib-util components used in PJSIP implementations. This flaw exists in versions prior to 2.7.1 and stems from improper handling of numeric header fields during SIP message parsing operations. The affected parameters include critical SIP headers such as cseq, ttl, and port fields that are routinely processed by SIP clients and servers. The vulnerability manifests when these numeric fields are parsed without adequate bounds checking, creating opportunities for malicious actors to craft specially formatted SIP messages that exploit the parsing logic.
The technical implementation of this vulnerability involves the parsing routines that process numeric values within SIP headers, where insufficient validation allows for integer overflow conditions to occur. When these parsed values exceed their allocated storage boundaries, they can overwrite adjacent memory locations, potentially leading to arbitrary code execution or application crashes. The flaw specifically affects the conversion processes between numeric and string representations of these header fields, where the overflow conditions can manifest during subsequent string conversions. This creates a pathway for attackers to manipulate the memory layout of the affected application through carefully crafted SIP messages containing malformed numeric header values.
The operational impact of CVE-2017-16872 extends across various network communication systems that rely on pjproject for SIP protocol handling, including VoIP phones, PBX systems, SIP proxies, and multimedia communication servers. Attackers can exploit this vulnerability by sending malicious SIP messages with crafted numeric header values that trigger the buffer overflow conditions during parsing. The potential consequences include complete system compromise, denial of service attacks, or unauthorized access to communication infrastructure. Given that pjproject is widely used in enterprise and telecommunications environments, the exploitability of this vulnerability poses significant risks to network security and service availability. The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and demonstrates characteristics consistent with ATT&CK technique T1203, involving exploitation of input validation weaknesses in network protocols.
Mitigation strategies for CVE-2017-16872 require immediate patching of affected systems to upgrade to pjproject version 2.7.1 or later, which contains the necessary fixes for the numeric header parsing routines. Organizations should implement network monitoring to detect suspicious SIP traffic patterns that may indicate exploitation attempts, while also configuring proper input validation at network boundaries to filter malformed SIP messages. Additional defensive measures include implementing rate limiting for SIP message processing, deploying intrusion detection systems specifically configured to identify SIP protocol anomalies, and conducting thorough security assessments of all systems utilizing pjproject components. The vulnerability serves as a reminder of the critical importance of proper input validation and bounds checking in protocol implementations, particularly for network-facing applications handling real-time communication protocols.