CVE-2009-0661 in WeeChat
Summary
by MITRE
Wee Enhanced Environment for Chat (WeeChat) 0.2.6 allows remote attackers to cause a denial of service (crash) via an IRC PRIVMSG command containing crafted color codes that trigger an out-of-bounds read.
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Analysis
by VulDB Data Team • 05/03/2025
The vulnerability identified as CVE-2009-0661 affects WeeChat version 0.2.6, a popular console-based IRC client that provides enhanced chat environments for users connecting to internet relay chat networks. This issue represents a critical security flaw that enables remote attackers to disrupt the normal operation of the application through carefully crafted malicious input. The vulnerability specifically targets the client's handling of IRC PRIVMSG commands, which are fundamental communication elements in IRC protocols used for private messaging between users.
The technical flaw manifests when WeeChat processes IRC PRIVMSG commands containing specially crafted color codes that exceed the bounds of allocated memory buffers. This out-of-bounds read condition occurs during the parsing and rendering of colored text within chat messages, where the application fails to properly validate the length and structure of color code sequences. The vulnerability stems from inadequate input sanitization and memory management within the client's text processing subsystem, allowing malicious actors to exploit the buffer handling mechanisms through crafted IRC messages.
From an operational perspective, this vulnerability creates a significant denial of service condition that can crash the WeeChat application, forcing users to restart the client and potentially lose ongoing chat sessions. The remote nature of the attack means that any user connected to an IRC network where the vulnerability exists can be affected, making it particularly dangerous in shared or public chat environments. Attackers can exploit this flaw by simply sending a malicious PRIVMSG command containing crafted color codes, requiring no authentication or privileged access to the target system.
The impact extends beyond simple application crashes as it can potentially be leveraged for more sophisticated attacks in environments where WeeChat is used in automated or networked configurations. This vulnerability aligns with CWE-125, which describes out-of-bounds read conditions in software implementations, and represents a classic example of memory safety issues that can lead to application instability. The flaw also relates to ATT&CK technique T1499.004, which covers network denial of service attacks that compromise system availability through application-level vulnerabilities.
Mitigation strategies should focus on immediate patching of the WeeChat application to version 0.3.0 or later, which includes proper bounds checking and input validation for color code processing. Administrators should also implement network-level filtering to prevent malformed PRIVMSG commands from reaching vulnerable clients, though this approach may impact legitimate functionality. Additionally, users should be educated about the risks of accepting messages from untrusted sources and the importance of keeping their IRC clients updated. The vulnerability highlights the critical importance of input validation in networked applications and demonstrates how seemingly benign features like colored text can become attack vectors when proper security measures are not implemented.