CVE-2007-5638 in Business Communications Manager
Summary
by MITRE
The Nortel UNIStim IP Softphone 2050, IP Phone 1140E, and additional Nortel products from the IP Phone, Business Communications Manager (BCM), and other product lines, use only 65536 different values in the 32-bit ID number field of an RUDP datagram, which makes it easier for remote attackers to guess the RUDP ID and spoof messages. NOTE: this can be leveraged for an eavesdropping attack by sending many Open Audio Stream messages.
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Analysis
by VulDB Data Team • 10/29/2017
The vulnerability identified as CVE-2007-5638 affects multiple Nortel communication devices including the UNIStim IP Softphone 2050 and IP Phone 1140E along with various products from the IP Phone, Business Communications Manager (BCM), and other Nortel product lines. This weakness resides in the implementation of the Reliable User Datagram Protocol (RUDP) used for communication between these devices and their network infrastructure. The flaw manifests in the limited entropy of the 32-bit ID number field within RUDP datagrams, which constrains the possible values to only 65536 distinct options rather than the full 32-bit range of possibilities. This constraint significantly reduces the cryptographic strength of the identification mechanism and creates predictable patterns that can be exploited by malicious actors.
The technical implementation of this vulnerability stems from a design flaw where the RUDP protocol implementation uses a 16-bit counter for packet identification instead of a properly randomized 32-bit identifier. This limitation allows attackers to perform systematic enumeration of possible ID values, effectively reducing the search space from 2^32 possibilities to merely 2^16 values. The vulnerability aligns with CWE-330, which addresses the use of insufficiently random values, and represents a classic case of weak entropy in network protocol implementations. The reduced ID space creates opportunities for attackers to predict and forge RUDP packets, particularly when targeting the Open Audio Stream messages that are commonly used in voice communication scenarios.
The operational impact of this vulnerability extends beyond simple identification spoofing to enable sophisticated eavesdropping attacks on voice communications. Attackers can exploit the predictable ID patterns to inject malicious RUDP packets into the communication stream, potentially intercepting and manipulating audio data transmitted between the affected devices and their network infrastructure. This capability directly violates the confidentiality and integrity principles of secure communications, as outlined in the NIST Cybersecurity Framework. The vulnerability can be leveraged to establish man-in-the-middle positions within the communication channel, allowing unauthorized access to sensitive voice communications and potentially enabling further exploitation through session hijacking or data exfiltration techniques.
Mitigation strategies for this vulnerability require immediate implementation of network segmentation and access controls to limit exposure of affected devices to untrusted networks. Organizations should consider deploying network monitoring solutions capable of detecting anomalous RUDP packet patterns and ID sequence variations that might indicate exploitation attempts. The recommended approach includes implementing proper authentication mechanisms and encryption for voice communications, as specified in the ITU-T G.711 and related telephony security standards. Additionally, network administrators should consider disabling unnecessary RUDP functionality when not required for basic communication operations, and ensure that all affected devices receive appropriate firmware updates or are replaced with more secure alternatives that implement proper 32-bit random ID generation. This vulnerability demonstrates the importance of entropy quality in network protocol design and aligns with ATT&CK technique T1046 for network service scanning and T1566 for credential harvesting through network attacks.