CVE-2003-0079 in hanterm-xf
Summary
by MITRE
The DEC UDK processing feature in the hanterm (hanterm-xf) terminal emulator before 2.0.5 allows attackers to cause a denial of service via a certain character escape sequence that causes the terminal to enter a tight loop.
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Analysis
by VulDB Data Team • 08/25/2025
The vulnerability described in CVE-2003-0079 represents a critical denial of service flaw within the DEC UDK processing feature of the hanterm terminal emulator, specifically affecting versions prior to 2.0.5. This issue manifests through a carefully crafted character escape sequence that triggers an infinite loop condition within the terminal's processing logic, effectively rendering the system unresponsive and preventing legitimate user interaction with the terminal interface.
The technical root cause of this vulnerability lies in the improper handling of escape sequences during the processing of DEC UDK (User Defined Keys) functionality. When the hanterm-xf terminal emulator receives a specific malformed escape sequence, its internal parsing mechanism enters a state where it continuously processes the same sequence without proper termination conditions. This tight loop behavior consumes excessive CPU resources and prevents the terminal from processing any other input or commands, creating a persistent denial of service condition that affects all users of the affected system.
From an operational impact perspective, this vulnerability presents significant risks to system availability and user productivity within environments that rely on the hanterm terminal emulator for Korean character set processing. The tight loop condition can persist indefinitely until the system is manually restarted or the terminal process is terminated, potentially affecting multiple users simultaneously if the terminal emulator is widely deployed. The vulnerability is particularly concerning in server environments or multi-user systems where terminal access is critical for system administration and user operations.
This flaw aligns with CWE-835, which specifically addresses the issue of infinite loops in software systems, and demonstrates how improper input validation and error handling can lead to denial of service conditions. The vulnerability also maps to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion, as the tight loop consumes system resources without proper bounds checking. Organizations implementing security controls should consider this vulnerability as part of their broader denial of service mitigation strategies, particularly in environments where terminal emulators process untrusted input from external sources.
The recommended remediation approach involves upgrading to hanterm version 2.0.5 or later, which includes proper bounds checking and termination conditions for escape sequence processing. Additionally, system administrators should implement input validation measures and monitor for unusual CPU usage patterns that might indicate exploitation attempts. Network segmentation and access controls can help limit the potential impact of exploitation by restricting access to vulnerable terminal systems. Regular security assessments should include verification of terminal emulator versions and configuration settings to ensure proper protection against similar vulnerabilities in other components of the system infrastructure.