CVE-2016-2369 in Pidgin
Summary
by MITRE
A NULL pointer dereference vulnerability exists in the handling of the MXIT protocol in Pidgin. Specially crafted MXIT data sent via the server could potentially result in a denial of service vulnerability. A malicious server can send a packet starting with a NULL byte triggering the vulnerability.
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Analysis
by VulDB Data Team • 04/20/2025
The vulnerability identified as CVE-2016-2369 represents a critical NULL pointer dereference flaw within Pidgin's MXIT protocol implementation, demonstrating a fundamental weakness in how the popular instant messaging client processes external protocol data. This vulnerability specifically affects the MXIT protocol handler, which is used for communication with MXIT servers, a messaging service that was popular in certain regions. The flaw manifests when Pidgin receives specially crafted MXIT data from a malicious server, creating a scenario where the application's memory management becomes compromised. The vulnerability is triggered by a packet that begins with a NULL byte, which serves as the primary attack vector for exploiting this weakness. This particular implementation error falls under the category of improper input validation and memory handling, making it particularly dangerous as it can be leveraged by remote attackers without requiring any special privileges or user interaction.
The technical exploitation of this vulnerability occurs through the manipulation of protocol parsing logic within Pidgin's MXIT plugin, where the application fails to properly validate incoming data before attempting to dereference pointers. When the MXIT protocol handler encounters a packet starting with a NULL byte, it attempts to process this data without adequate null checks, leading to a situation where the program tries to access memory at address zero. This NULL pointer dereference results in an immediate crash of the Pidgin application, effectively creating a denial of service condition that prevents legitimate users from accessing their messaging services. The vulnerability is classified as a CWE-476 NULL Pointer Dereference, which is a well-documented weakness in software development practices where programs fail to check for null values before attempting to use pointers. This specific weakness is particularly dangerous in client applications like Pidgin that must process untrusted data from external servers, as it provides a direct path for remote attackers to disrupt service availability.
The operational impact of CVE-2369 extends beyond simple service disruption, as it represents a fundamental flaw in the security architecture of Pidgin's protocol handling capabilities. When exploited, this vulnerability allows malicious actors to remotely crash the messaging client, potentially disrupting communications for users who rely on MXIT services. The attack requires minimal technical expertise, as it only necessitates sending a properly formatted packet containing a NULL byte, making it an attractive vector for attackers seeking to cause disruption. From an adversary perspective, this vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service, as it enables the creation of a persistent disruption to user access. The vulnerability also demonstrates poor defensive programming practices that should be addressed through proper input sanitization, error handling, and memory management protocols. Users who are actively connected to MXIT servers when the malicious packet is received will experience immediate application termination, while the broader impact includes potential data loss and service unavailability that could affect business communications or personal messaging reliability.
Mitigation strategies for CVE-2016-2369 must address both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities. The most effective immediate solution involves applying the official security patch released by the Pidgin development team, which includes proper null pointer validation and input sanitization for MXIT protocol data. System administrators should also implement network monitoring to detect and block suspicious MXIT packets that begin with NULL bytes, while users should avoid connecting to untrusted MXIT servers until the vulnerability is patched. Organizations should consider implementing network segmentation to isolate messaging services from critical infrastructure, reducing the potential impact of such vulnerabilities. The vulnerability highlights the importance of robust defensive programming practices and emphasizes the need for comprehensive input validation across all protocol handlers within messaging applications. Additionally, regular security audits of third-party plugins and protocol implementations should be conducted to identify and remediate similar weaknesses before they can be exploited by malicious actors. This vulnerability serves as a reminder of the critical importance of memory safety in client applications that must process untrusted data, and the necessity of implementing proper error handling mechanisms to prevent crashes that could be exploited for denial of service attacks.