CVE-2020-9759 in WeeChat
Summary
by MITRE
An issue was discovered in WeeChat before 2.7.1 (0.4.0 to 2.7 are affected). A malformed message 352 (who) can cause a NULL pointer dereference in the callback function, resulting in a crash.
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Analysis
by VulDB Data Team • 05/11/2024
The vulnerability identified as CVE-2020-9759 represents a critical NULL pointer dereference flaw within the WeeChat IRC client software. This issue affects versions ranging from 0.4.0 through 2.7, with the specific exploitation occurring through malformed message 352 responses during WHO command processing. The vulnerability resides in the callback function responsible for handling IRC protocol responses, where improper input validation allows maliciously crafted data to trigger unexpected behavior in the application's memory management system.
The technical exploitation of this vulnerability occurs when WeeChat receives a malformed WHO reply message that contains invalid or unexpected data structures. During normal operation, the client processes WHO commands to retrieve information about IRC users in channels, but the callback function that handles the 352 message type fails to properly validate incoming data before attempting to access memory locations. This failure results in a NULL pointer dereference, which causes the application to crash and terminate unexpectedly. The flaw directly maps to CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations.
The operational impact of this vulnerability extends beyond simple application instability, as it can be leveraged by remote attackers to perform denial of service attacks against WeeChat users. Since IRC clients often operate in networked environments where users may connect to untrusted servers, an attacker could craft malicious WHO replies that would crash the client whenever a user attempts to view channel information. This creates a persistent threat vector that could be exploited in various scenarios including public IRC servers, private network environments, or even through compromised channels within trusted networks.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers "Utilities: Endpoint Denial of Service" and demonstrates how seemingly benign protocol interactions can be weaponized for system disruption. The flaw represents a classic example of insufficient input validation in network protocols, where the application assumes all incoming data conforms to expected formats without proper sanitization checks. Organizations using WeeChat for IRC communications should consider this vulnerability as a significant risk, particularly in environments where network security cannot be fully trusted or where users may encounter untrusted IRC servers.
Mitigation strategies for CVE-2020-9759 primarily involve immediate patching of WeeChat installations to version 2.7.1 or later, where the NULL pointer dereference has been resolved through proper input validation and memory access checks. Additionally, network administrators should implement monitoring for unusual WHO command responses and consider deploying intrusion detection systems that can identify malformed IRC protocol traffic. The vulnerability serves as a reminder of the importance of robust input validation in network applications and highlights the necessity of regular security updates in client software that processes untrusted network data. Organizations should also consider implementing network segmentation to limit exposure to potentially malicious IRC traffic and establish incident response procedures for handling application crashes resulting from protocol-based attacks.