CVE-2018-15126 in LibVNC
Summary
by MITRE
LibVNC before commit 73cb96fec028a576a5a24417b57723b55854ad7b contains heap use-after-free vulnerability in server code of file transfer extension that can result remote code execution
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Analysis
by VulDB Data Team • 06/19/2023
The heap use-after-free vulnerability in LibVNC represents a critical security flaw that affects remote desktop protocol implementations across numerous systems. This vulnerability specifically resides within the server code of the file transfer extension, making it particularly dangerous for environments where remote desktop services are extensively utilized. The vulnerability was identified in versions of LibVNC prior to commit 73cb96fec028a576a5a24417b57723b55854ad7b, indicating that developers had not yet patched this memory management issue that could be exploited by malicious actors.
The technical nature of this flaw stems from improper memory handling within the file transfer functionality of the VNC server implementation. When processing file transfer requests, the system allocates memory for file data structures and subsequently frees this memory upon completion of operations. However, a race condition or improper pointer management allows an attacker to potentially access or manipulate memory that has already been freed, creating a use-after-free condition. This memory corruption vulnerability can be exploited through carefully crafted file transfer requests that trigger the vulnerable code path, allowing attackers to manipulate the memory layout and potentially execute arbitrary code on the target system.
The operational impact of this vulnerability extends beyond simple remote code execution, as it represents a significant threat to remote desktop security infrastructure. Systems utilizing LibVNC for remote access, including enterprise networks, cloud environments, and virtual desktop infrastructures, face potential compromise when affected versions are deployed. The vulnerability could be exploited by remote attackers without authentication, making it particularly dangerous in environments where VNC servers are exposed to untrusted networks or internet-facing services. Attackers could leverage this flaw to gain full system control, escalate privileges, or establish persistent access points within target networks, making it a high-priority security concern for organizations relying on remote desktop solutions.
Mitigation strategies for this vulnerability require immediate patching of affected LibVNC installations to versions containing the fix from commit 73cb96fec028a576a5a24417b57723b55854ad7b or later. Organizations should conduct comprehensive inventory assessments to identify all systems running vulnerable versions of LibVNC, including those in legacy systems or specialized applications that may not receive regular updates. Network segmentation and access controls should be implemented to limit exposure of VNC services to trusted networks only, while monitoring systems should be configured to detect unusual file transfer activity that might indicate exploitation attempts. Additionally, security teams should consider implementing intrusion detection systems that can identify patterns consistent with use-after-free exploitation attempts, and regular security audits should verify that all remote desktop implementations have been updated to secure versions.
This vulnerability aligns with CWE-416, which describes use-after-free conditions in software systems, and represents a classic example of memory safety issues that can lead to arbitrary code execution. The attack pattern follows ATT&CK technique T1059.007 for remote code execution through network services, and could potentially map to T1071.004 for application layer protocols involving file transfer operations. Organizations should also consider the broader implications of this vulnerability within their security posture, as it demonstrates the importance of proper memory management in network service implementations and highlights the need for comprehensive security testing of protocol implementations.