CVE-2018-5208 in irssi
Summary
by MITRE
In Irssi before 1.0.6, a calculation error in the completion code could cause a heap buffer overflow when completing certain strings.
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Analysis
by VulDB Data Team • 12/20/2019
The vulnerability identified as CVE-2018-5208 represents a critical heap buffer overflow flaw within the Irssi IRC client software family. This issue affects versions prior to 1.0.6 and stems from a calculation error within the completion code module that handles tab completion functionality. The Irssi client, widely used for IRC communications, processes user input through various completion mechanisms including nickname suggestions and command auto-completion. When users engage these features with specific input strings, the flawed calculation logic causes the software to allocate insufficient memory buffers for storing completion results. This memory miscalculation creates a condition where subsequent data writes exceed allocated buffer boundaries, resulting in heap corruption that can potentially be exploited by malicious actors.
The technical implementation of this vulnerability resides in the completion subsystem's memory management routines where input string lengths are improperly calculated or validated before buffer allocation. According to CWE-121, this corresponds to a stack-based buffer overflow condition, though the heap-based nature of the actual flaw makes it more complex to exploit. The vulnerability manifests when the completion engine encounters certain character sequences that trigger the miscalculated buffer size, leading to memory corruption that could allow attackers to execute arbitrary code or cause denial of service conditions. The flaw specifically impacts the client-side operation during interactive sessions where users rely on tab completion features, making it particularly dangerous in environments where users frequently interact with the application.
The operational impact of CVE-2018-5208 extends beyond simple denial of service scenarios to encompass potential remote code execution capabilities. Attackers could exploit this vulnerability by crafting malicious input strings that, when processed through Irssi's completion system, trigger the buffer overflow condition. This would enable them to overwrite adjacent memory locations, potentially allowing for code injection attacks or privilege escalation. The vulnerability affects not only individual user sessions but also networked environments where multiple users interact through shared IRC channels, as the compromised client could serve as a vector for broader network compromise. According to ATT&CK framework technique T1059, this vulnerability could facilitate command and control operations, while T1133 relates to the exploitation of client-side vulnerabilities in network communication tools.
Mitigation strategies for CVE-2018-5208 focus primarily on upgrading to Irssi version 1.0.6 or later, which contains the patched completion code that properly validates input string lengths before buffer allocation. System administrators should implement immediate patch management procedures to ensure all affected installations receive the necessary updates. Additional protective measures include implementing network segmentation to limit exposure, monitoring for suspicious completion patterns, and establishing robust input validation routines within IRC client configurations. The vulnerability highlights the importance of proper memory management in client-side applications and underscores the need for thorough code review processes, particularly in modules handling user input and completion functionality. Organizations should also consider implementing runtime protections such as address space layout randomization and stack canaries to reduce exploitability even if other mitigations fail.