CVE-2004-1940 in Kphone
Summary
by MITRE
sipclient.cpp in KPhone 4.0.1 and earlier allows remote attackers to cause a denial of service (crash) via a STUN response packet with a large attrLen value that causes an out-of-bounds read.
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Analysis
by VulDB Data Team • 01/11/2025
The vulnerability described in CVE-2004-1940 affects KPhone 4.0.1 and earlier versions, specifically within the sipclient.cpp component that handles Session Initiation Protocol communication. This issue represents a classic buffer overflow condition that manifests as an out-of-bounds read operation when processing STUN response packets. The flaw occurs during the parsing of network traffic where the application fails to properly validate the attribute length field in STUN packets, allowing malicious actors to craft specially crafted packets that trigger memory access violations.
The technical implementation of this vulnerability stems from insufficient input validation in the STUN protocol handling code. When KPhone receives a STUN response packet, it attempts to parse the attribute length field without proper bounds checking, which allows an attacker to specify an excessively large attrLen value. This causes the application to attempt reading memory beyond the allocated buffer boundaries, resulting in a segmentation fault or application crash. The vulnerability is categorized under CWE-125 as an out-of-bounds read, which represents a fundamental memory safety issue that can lead to system instability and potential exploitation for more serious attacks.
From an operational perspective, this vulnerability presents a significant denial of service threat to users of KPhone applications, particularly in environments where VoIP services are critical for communication. The remote nature of the attack means that any user connected to a network where malicious actors can inject packets can potentially disrupt service. The impact extends beyond simple service interruption as the crash behavior can be exploited to create persistent availability issues for VoIP communications, affecting both individual users and enterprise communication systems that rely on KPhone for voice services.
The attack vector for this vulnerability aligns with the ATT&CK framework's T1498 technique for network denial of service, where adversaries target application-level protocols to disrupt services. Network administrators should consider implementing network segmentation and packet filtering to prevent unauthorized access to VoIP systems. The vulnerability demonstrates the importance of proper input validation in network protocol implementations, as highlighted by the CWE-20 standard for input validation flaws. Organizations should prioritize patch management for legacy VoIP applications and implement monitoring solutions to detect anomalous STUN traffic patterns that may indicate attempted exploitation of this vulnerability.
Mitigation strategies should include immediate patching of affected KPhone versions to address the buffer overflow condition, implementing network-level protections such as firewalls that filter suspicious STUN packets, and establishing robust application monitoring to detect crash patterns. The fix should involve proper bounds checking of attribute length fields in STUN packet parsing, ensuring that any value exceeding reasonable limits is rejected rather than processed, thereby preventing the out-of-bounds memory access that leads to application crashes.