CVE-2014-8240 in TigerVNC
Summary
by MITRE
Integer overflow in TigerVNC allows remote VNC servers to cause a denial of service (crash) and possibly execute arbitrary code via vectors related to screen size handling, which triggers a heap-based buffer overflow, a similar issue to CVE-2014-6051.
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Analysis
by VulDB Data Team • 03/30/2022
The vulnerability identified as CVE-2014-8240 represents a critical integer overflow flaw within the TigerVNC implementation that affects remote VNC servers and presents significant security implications for affected systems. This vulnerability stems from improper handling of screen size parameters during the VNC connection process, creating a pathway for malicious actors to manipulate the system's memory management through carefully crafted input sequences. The flaw specifically manifests when the VNC server processes screen dimension values that exceed the maximum representable integer values, leading to unexpected behavior in memory allocation and data handling operations.
The technical exploitation of this vulnerability occurs through heap-based buffer overflow conditions that arise from the integer overflow during screen size calculations. When a remote attacker sends malicious screen dimension parameters to a vulnerable TigerVNC server, the system's integer arithmetic fails to properly validate or handle the overflow condition, resulting in corrupted heap memory structures. This memory corruption directly translates to a denial of service condition where the VNC server crashes and becomes unavailable to legitimate users, while simultaneously creating opportunities for arbitrary code execution through carefully crafted memory corruption patterns that can be leveraged to gain unauthorized system access. The vulnerability's similarity to CVE-2014-6051 demonstrates a pattern of integer overflow issues within VNC implementations that affect multiple components of the remote desktop protocol stack.
From an operational impact perspective, this vulnerability creates substantial risk for organizations relying on VNC services for remote system administration, desktop management, and remote access operations. The denial of service component immediately compromises availability of critical remote access services, potentially disrupting business operations and requiring immediate system restoration. The arbitrary code execution capability presents even greater risk as attackers can potentially establish persistent access to systems, escalate privileges, or deploy additional malicious payloads. The vulnerability affects both the server and client components of TigerVNC implementations, meaning that systems acting as VNC servers are at risk of being compromised by remote attackers, while client systems may also face exploitation if they connect to malicious VNC servers. This makes the vulnerability particularly dangerous in enterprise environments where VNC is commonly used for remote support, system administration, and IT management operations.
Organizations should implement immediate mitigations including applying the latest security patches from TigerVNC vendors, implementing network segmentation to limit VNC access to trusted networks, and deploying intrusion detection systems to monitor for suspicious VNC connection patterns. The vulnerability aligns with several ATT&CK techniques including T1021.001 for remote services and T1059.007 for command and scripting interpreter, while the integer overflow behavior corresponds to CWE-190, which specifically addresses integer overflow conditions that can lead to memory corruption. System administrators should also consider disabling unnecessary VNC services, implementing strong authentication mechanisms, and monitoring for unusual screen size parameter values that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper input validation and integer overflow protection in network services, particularly those handling user-supplied parameters that directly influence memory allocation and system behavior.