CVE-1999-0939 in Linux
Summary
by MITRE
Denial of service in Debian IRC Epic/epic4 client via a long string.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-0939 represents a classic denial of service flaw affecting the Debian IRC Epic/epic4 client software. This issue manifests when the client receives a specially crafted long string input that triggers a buffer overflow condition within the application's memory management routines. The vulnerability specifically impacts the epic4 IRC client version distributed through Debian operating systems, making it a significant concern for users relying on this particular software stack for internet relay chat communications.
The technical flaw stems from inadequate input validation and buffer management within the IRC client's string handling mechanisms. When processing network messages containing excessively long strings, the application fails to properly bounds-check the input data before attempting to store or process it in memory buffers. This lack of proper input sanitization creates a condition where maliciously crafted network traffic can cause the client application to overwrite adjacent memory locations, leading to unpredictable behavior including application crashes and complete service unavailability. The vulnerability operates at the application layer and requires only network access to exploit, making it particularly dangerous in networked environments where users may encounter malicious or malformed IRC messages.
The operational impact of this vulnerability extends beyond simple service disruption, as it can effectively render IRC communication channels unusable for affected clients. System administrators and end users who rely on the epic4 IRC client for critical communications may experience complete loss of connectivity to IRC networks, forcing them to restart client applications or switch to alternative IRC clients. This denial of service condition can be particularly disruptive in collaborative environments where real-time communication is essential, potentially causing significant operational downtime and productivity losses. The vulnerability affects the availability aspect of the CIA security triad by preventing legitimate users from accessing the service they depend upon.
Mitigation strategies for CVE-1999-0939 should focus on both immediate remediation and long-term architectural improvements. The primary solution involves updating to patched versions of the epic4 IRC client that include proper input validation and buffer overflow protection mechanisms. System administrators should also implement network-level filtering to prevent malformed IRC traffic from reaching client systems, though this approach provides only partial protection. From a cybersecurity perspective, this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and demonstrates the importance of implementing secure coding practices as outlined in the software security principles of the OWASP Top Ten. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities, while maintaining regular security updates and patch management procedures to address similar issues proactively. The ATT&CK framework categorizes this vulnerability under the T1499 category for network denial of service, highlighting the need for comprehensive network security measures to protect against such attacks.