CVE-2017-7392 in TigerVNC
Summary
by MITRE
In TigerVNC 1.7.1 (SSecurityVeNCrypt.cxx SSecurityVeNCrypt::SSecurityVeNCrypt), an unauthenticated client can cause a small memory leak in the server.
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Analysis
by VulDB Data Team • 11/24/2022
The vulnerability identified as CVE-2017-7392 resides within the TigerVNC 1.7.1 implementation, specifically in the SSecurityVeNCrypt.cxx source file within the SSecurityVeNCrypt::SSecurityVeNCrypt class. This memory leak occurs during the VNC authentication process when an unauthenticated client establishes a connection to the VNC server. The flaw represents a denial of service vulnerability that can be exploited by remote attackers without requiring any authentication credentials or privileged access to the system. The vulnerability manifests as a gradual accumulation of memory consumption on the VNC server, potentially leading to system instability or complete service exhaustion over time. The technical implementation flaw stems from inadequate memory management during the authentication handshake process where the server fails to properly release allocated memory resources when handling malformed or unexpected client connection sequences. This type of vulnerability falls under the CWE-401 category of inadequate resource management, specifically memory leaks that occur during protocol handling. The ATT&CK framework would classify this vulnerability under T1499.004 for network denial of service attacks, as it targets the availability aspect of the VNC service by consuming system resources through improper memory handling. The operational impact of this vulnerability extends beyond simple resource consumption, as it can be leveraged by malicious actors to perform sustained denial of service attacks against VNC servers in corporate environments where remote desktop access is commonly utilized. The vulnerability is particularly concerning in enterprise settings where VNC servers may be exposed to untrusted networks or where multiple concurrent connections are expected, as the memory leak can compound over time and potentially lead to system crashes or service unavailability. The attack surface is broad as any client capable of establishing a VNC connection can trigger the memory leak, making it an attractive target for automated exploitation tools that can repeatedly initiate connections to consume server resources. Organizations utilizing TigerVNC 1.7.1 should prioritize patching this vulnerability as it represents a straightforward memory management issue that can be exploited without specialized knowledge or privileged access. The recommended mitigation involves upgrading to a patched version of TigerVNC where the memory allocation and deallocation routines have been properly implemented to ensure all allocated resources are correctly released during the authentication process. Additionally, network segmentation and access control measures should be implemented to limit exposure of VNC servers to untrusted networks, reducing the attack surface for this particular vulnerability. Security monitoring should include tracking of memory consumption patterns on VNC servers to detect potential exploitation attempts. The vulnerability demonstrates the importance of proper resource management in network protocol implementations and serves as a reminder that even seemingly benign authentication processes can contain critical memory management flaws that can be exploited for denial of service attacks.