CVE-2019-15692 in TigerVNC
Summary
by MITRE
TigerVNC version prior to 1.10.1 is vulnerable to heap buffer overflow. Vulnerability could be triggered from CopyRectDecoder due to incorrect value checks. Exploitation of this vulnerability could potentially result into remote code execution. This attack appear to be exploitable via network connectivity.
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Analysis
by VulDB Data Team • 03/17/2024
The vulnerability identified as CVE-2019-15692 represents a critical heap buffer overflow flaw within TigerVNC software versions prior to 1.10.1. This vulnerability resides within the CopyRectDecoder component, which is responsible for handling rectangular copy operations during remote desktop sessions. The flaw stems from inadequate validation of input values during the decoding process, creating a condition where maliciously crafted data can cause memory corruption. The vulnerability's classification aligns with CWE-121, heap-based buffer overflow, and demonstrates the classic pattern of insufficient bounds checking in memory management operations. The attack vector requires only network connectivity, making it particularly dangerous as it can be exploited remotely without requiring physical access to the target system.
The technical implementation of this vulnerability occurs when the CopyRectDecoder processes incoming data packets containing rectangular copy instructions. The decoder fails to properly validate the dimensions and coordinates specified in these packets, allowing an attacker to provide values that exceed the allocated buffer boundaries. This misconfiguration enables an attacker to write data beyond the intended memory allocation, potentially overwriting adjacent memory regions including function pointers, return addresses, or other critical control data. The heap corruption resulting from this overflow can be leveraged to execute arbitrary code with the privileges of the affected VNC server process, typically running with elevated system permissions. This exploitation scenario directly maps to the ATT&CK technique T1059.007 for remote code execution through network services.
The operational impact of this vulnerability extends beyond simple remote code execution, as it represents a serious threat to enterprise network security infrastructure. VNC servers are commonly deployed in corporate environments for remote administration and support, making them attractive targets for attackers seeking persistent access to internal networks. The vulnerability's network-based exploitation capability means that attackers can target exposed VNC services without requiring prior authentication, potentially enabling lateral movement within networks where VNC servers serve as entry points. Organizations relying on older TigerVNC versions face significant risk of unauthorized system compromise, data exfiltration, and potential use as launch points for broader network attacks. The vulnerability's severity classification as high-risk stems from both its remote exploitability and the potential for privilege escalation, particularly when VNC servers operate with administrative privileges.
Mitigation strategies for CVE-2019-15692 center primarily on upgrading to TigerVNC version 1.10.1 or later, which includes proper bounds checking and input validation within the CopyRectDecoder component. Network segmentation and firewall rules should be implemented to restrict access to VNC services, limiting exposure to trusted networks only. Organizations should also consider implementing additional security controls such as VPN access for VNC connections, multi-factor authentication, and regular security assessments of remote desktop services. The vulnerability's remediation aligns with standard security practices outlined in NIST SP 800-40 and ISO/IEC 27001, emphasizing the importance of timely patch management and vulnerability remediation. Additionally, monitoring for suspicious network traffic patterns and implementing intrusion detection systems can help identify potential exploitation attempts targeting this vulnerability, providing defense-in-depth protection against adversaries seeking to leverage this heap buffer overflow for unauthorized access.