CVE-2008-0610 in UltraVNC
Summary
by MITRE
Stack-based buffer overflow in the ClientConnection::NegotiateProtocolVersion function in vncviewer/ClientConnection.cpp in vncviewer for UltraVNC 1.0.2 and 1.0.4 before 01252008, when in LISTENING mode or when using the DSM plugin, allows remote attackers to execute arbitrary code or cause a denial of service (crash) via a modified size value.
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Analysis
by VulDB Data Team • 07/25/2024
The vulnerability identified as CVE-2008-0610 represents a critical stack-based buffer overflow in the UltraVNC remote desktop software client component. This flaw exists within the ClientConnection::NegotiateProtocolVersion function located in vncviewer/ClientConnection.cpp, specifically affecting UltraVNC versions 1.0.2 and 1.0.4 prior to the 01252008 patch release. The vulnerability manifests when the vncviewer application operates in LISTENING mode or when utilizing the DSM plugin functionality, creating a dangerous attack surface that can be exploited by remote adversaries.
The technical implementation of this vulnerability stems from improper input validation within the protocol version negotiation process. When the client receives a modified size value during connection establishment, the application fails to properly bounds-check the incoming data before copying it to a fixed-size stack buffer. This classic buffer overflow condition allows an attacker to overwrite adjacent stack memory, potentially corrupting program execution flow and enabling arbitrary code execution. The flaw operates at the protocol level where the client expects specific data formats but does not adequately validate the size parameter, leading to memory corruption that can be leveraged for privilege escalation or system compromise.
The operational impact of this vulnerability extends beyond simple denial of service to encompass full system compromise capabilities. Remote attackers can exploit this weakness to execute arbitrary code with the privileges of the affected vncviewer process, which typically runs with the same permissions as the user who initiated the connection. This could result in complete system takeover, data exfiltration, or establishment of persistent backdoors. The vulnerability's exploitation is particularly concerning because it affects the client-side component of UltraVNC, meaning that simply connecting to an attacker-controlled server could trigger the exploit, making it a significant threat vector for unauthorized access scenarios.
Security professionals should recognize this vulnerability as mapping to CWE-121 Stack-based Buffer Overflow, which is classified under the Common Weakness Enumeration framework for buffer overflow conditions where data is copied to a stack buffer without proper bounds checking. From an ATT&CK framework perspective, this vulnerability aligns with T1210 Exploitation of Remote Services and T1059 Command and Scripting Interpreter techniques, as it enables remote code execution through network-based attack vectors. Organizations using affected UltraVNC versions should immediately implement mitigations including patching to the latest available version, network segmentation to limit exposure, and monitoring for unusual connection patterns or attempted exploitation attempts. The vulnerability demonstrates the critical importance of input validation in network-facing applications and serves as a reminder of the potential for seemingly benign protocol negotiation functions to become attack vectors when proper security controls are not implemented.