CVE-2015-4059 in Terminal Emulation
Summary
by MITRE
Heap-based buffer overflow in the License Server (LicenseServer.exe) in Wavelink Terminal Emulation (TE) allows remote attackers to execute arbitrary code via a large HTTP header.
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Analysis
by VulDB Data Team • 04/02/2019
The vulnerability identified as CVE-2015-4059 represents a critical heap-based buffer overflow within the License Server component of Wavelink Terminal Emulation software. This flaw exists in the LicenseServer.exe executable which is responsible for managing licensing operations within the terminal emulation environment. The vulnerability manifests when the software processes HTTP headers sent over the network, specifically when these headers exceed the allocated buffer space. The heap-based nature of this overflow indicates that memory allocated on the heap for processing HTTP header data can be overwritten beyond its intended boundaries, creating opportunities for malicious code execution.
The technical implementation of this vulnerability stems from insufficient input validation and boundary checking within the HTTP header processing logic of the License Server. When remote attackers craft specially formatted HTTP headers containing excessive data, the application fails to properly validate the length of these headers before copying them into fixed-size buffers allocated in heap memory. This classic buffer overflow condition occurs because the software does not implement proper bounds checking or input sanitization mechanisms before handling potentially malicious HTTP header data. The flaw is particularly dangerous as it operates over network connections, allowing attackers to remotely exploit the vulnerability without requiring local system access.
From an operational impact perspective, this vulnerability presents a severe threat to organizations relying on Wavelink Terminal Emulation for their terminal server operations. Remote code execution capabilities enable attackers to gain complete control over affected systems, potentially leading to data breaches, system compromise, and unauthorized access to sensitive terminal sessions. The vulnerability affects the core licensing functionality of the terminal emulation software, which may be exposed to the internet or accessible from untrusted networks. Organizations using this software in production environments face significant risk of unauthorized access and potential system infiltration, particularly when the License Server is configured to accept connections from external sources.
Security professionals should consider this vulnerability in relation to CWE-121, which describes heap-based buffer overflow conditions, and align it with ATT&CK technique T1059 for remote code execution. The attack surface for this vulnerability extends beyond simple exploitation to include potential lateral movement within networks where compromised systems may serve as entry points for broader attacks. Organizations should immediately implement network segmentation to isolate the affected License Server components and restrict access to only trusted administrative networks. Patch management procedures should be prioritized to deploy vendor-provided security updates, while monitoring systems should be enhanced to detect anomalous HTTP header patterns that may indicate exploitation attempts. The vulnerability also highlights the importance of secure coding practices, particularly around input validation and memory management, as recommended in OWASP Top 10 security guidelines for preventing buffer overflow conditions in network-facing applications.