CVE-2011-1775 in TigerVNC
Summary
by MITRE
The CSecurityTLS::processMsg function in common/rfb/CSecurityTLS.cxx in the vncviewer component in TigerVNC 1.1beta1 does not properly verify the server s X.509 certificate, which allows man-in-the-middle attackers to spoof a TLS VNC server via an arbitrary certificate.
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Analysis
by VulDB Data Team • 01/13/2025
The vulnerability identified as CVE-2011-1775 resides within the TigerVNC 1.1beta1 software suite, specifically within the vncviewer component's CSecurityTLS::processMsg function located in common/rfb/CSecurityTLS.cxx. This flaw represents a critical weakness in the X.509 certificate validation mechanism that governs secure communication between VNC clients and servers. The vulnerability stems from insufficient certificate verification procedures that fail to properly validate the authenticity and legitimacy of server certificates presented during TLS handshakes.
The technical implementation flaw manifests when the CSecurityTLS::processMsg function processes incoming TLS messages without adequately examining the server certificate's trust chain, validity period, or proper signing authority. This incomplete verification process creates a pathway for malicious actors to perform man-in-the-middle attacks by presenting arbitrary certificates that appear legitimate to the vulnerable client. The vulnerability directly violates fundamental security principles of certificate-based authentication and TLS protocol compliance, as defined by industry standards including CWE-295 which addresses improper certificate validation.
From an operational perspective, this vulnerability exposes VNC sessions to significant risk of interception and manipulation by attackers who can establish fake VNC servers that appear authentic to legitimate clients. The impact extends beyond simple data theft to include potential system compromise, unauthorized access to graphical desktop environments, and complete control over targeted systems. The vulnerability affects organizations relying on VNC for remote administration, as it undermines the cryptographic security guarantees that TLS is designed to provide. Attackers exploiting this vulnerability can intercept, modify, or redirect VNC traffic without detection, making it particularly dangerous for enterprise environments where VNC is commonly used for remote system management.
The security implications of CVE-2011-1775 align with ATT&CK technique T1046 which covers network service scanning and T1566 which addresses credential harvesting through social engineering. Organizations should implement immediate mitigations including upgrading to patched versions of TigerVNC, disabling insecure VNC configurations, and implementing additional network-level security controls such as firewalls and network segmentation. The vulnerability also highlights the importance of proper certificate validation practices and demonstrates the critical need for thorough security testing of cryptographic implementations. System administrators should also consider implementing certificate pinning mechanisms and monitoring for unusual certificate validation behaviors in network traffic logs to detect potential exploitation attempts.