CVE-2024-42458 in VNC
Summary
by MITRE • 08/02/2024
server.c in Neat VNC (aka neatvnc) before 0.8.1 does not properly validate the security type, a related issue to CVE-2006-2369.
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Analysis
by VulDB Data Team • 09/06/2024
The vulnerability identified as CVE-2024-42458 affects Neat VNC server versions prior to 0.8.1, specifically within the server.c component where inadequate validation of security types exists. This flaw represents a regression or continuation of issues similar to CVE-2006-2369, which historically demonstrated weaknesses in VNC security type handling. The vulnerability stems from insufficient input validation mechanisms that fail to properly verify the legitimacy and compatibility of security types presented during the VNC connection establishment process. This type of flaw falls under CWE-20, which encompasses improper input validation, and represents a critical weakness in the authentication and authorization framework of the VNC server implementation. The security type validation failure creates a potential attack surface where malicious actors could exploit the lack of proper validation to bypass authentication mechanisms or manipulate the security negotiation process.
The technical exploitation of this vulnerability occurs during the initial VNC handshake when the server receives security type information from connecting clients. Without proper validation, the server may accept invalid or unexpected security type values that could lead to improper authentication handling or privilege escalation opportunities. This weakness allows attackers to potentially manipulate the security negotiation process, possibly enabling unauthorized access to VNC sessions or bypassing intended security controls. The vulnerability specifically targets the server-side validation logic in the neatvnc implementation, where security type selection should be strictly validated against known and supported security protocols. This type of issue aligns with ATT&CK technique T1110 which covers password spraying and credential access through protocol manipulation, and also relates to T1071 which covers application layer protocol usage for command and control communications.
The operational impact of CVE-2024-42458 extends beyond simple authentication bypass scenarios, potentially enabling attackers to perform session hijacking or escalate privileges within VNC environments. Organizations utilizing Neat VNC servers in production environments face significant risk from this vulnerability, particularly in scenarios where VNC is used for remote administration or system management. The vulnerability could be exploited by remote attackers without requiring prior authentication, making it particularly dangerous in exposed VNC server deployments. Security monitoring becomes more complex as the vulnerability may not generate obvious error messages or log entries, potentially allowing attackers to operate undetected. The risk is amplified in environments where VNC servers are configured with weak or default credentials, as the validation bypass could enable attackers to progress from initial access to full system compromise.
Mitigation strategies for CVE-2024-42458 primarily involve upgrading to Neat VNC version 0.8.1 or later, which contains the necessary security patches to address the improper validation issue. Organizations should implement network segmentation to limit exposure of VNC servers to trusted networks only, while also ensuring that VNC services are not exposed to the public internet. Additional protective measures include implementing strong authentication mechanisms such as two-factor authentication, using VPNs or bastion hosts for VNC access, and deploying network monitoring tools to detect anomalous VNC connection patterns. Security teams should also review and audit existing VNC configurations to ensure that only necessary security types are enabled and that proper access controls are implemented. Regular vulnerability scanning and penetration testing should be conducted to identify potential exploitation of this and similar vulnerabilities within the VNC ecosystem, with particular attention to the security type validation mechanisms in all VNC implementations. The fix implemented in version 0.8.1 addresses the core validation logic to ensure that only properly defined and supported security types are accepted during the VNC connection process, thereby preventing the exploitation vector that existed in previous versions.