CVE-2011-4939 in pidgin
Summary
by MITRE
The pidgin_conv_chat_rename_user function in gtkconv.c in Pidgin before 2.10.2 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) by changing a nickname while in an XMPP chat room.
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Analysis
by VulDB Data Team • 11/30/2021
The vulnerability identified as CVE-2011-4939 represents a critical denial of service flaw within the Pidgin instant messaging client that affected versions prior to 2.10.2. This issue specifically resides in the gtkconv.c file within the pidgin_conv_chat_rename_user function, which handles nickname changes in chat room environments. The vulnerability manifests when a user attempts to rename another participant's nickname while engaged in an XMPP chat room, creating a scenario where the application fails to properly validate input parameters before attempting to process the rename operation.
The technical implementation of this flaw stems from a NULL pointer dereference condition that occurs when the function receives malformed or unexpected input during nickname modification operations. When an attacker manipulates the chat room environment to trigger a nickname change while the target user's data structure is in an inconsistent state, the application attempts to access a null memory reference, leading to an immediate application crash. This behavior directly aligns with CWE-476, which categorizes NULL pointer dereference vulnerabilities as a fundamental flaw in memory management that can result in system instability and service disruption. The vulnerability operates at the application layer and requires minimal privileges to exploit, making it particularly dangerous in environments where Pidgin serves as a communication platform for multiple users.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged to create persistent denial of service conditions within XMPP chat environments. Attackers can repeatedly trigger the crash condition to prevent legitimate users from participating in chat conversations, effectively disrupting communication channels that may be critical for business operations or collaborative activities. In enterprise environments where Pidgin is used for internal communications, this vulnerability could lead to significant productivity losses and potential security implications if attackers use it to target specific users or channels. The vulnerability's exploitation does not require elevated privileges and can be executed through standard chat room interactions, making it accessible to anyone with network access to the affected Pidgin client. From an attacker perspective, this flaw maps to ATT&CK technique T1499.004 which covers network denial of service attacks, where the adversary leverages application-level vulnerabilities to disrupt services.
Mitigation strategies for CVE-2011-4939 primarily focus on immediate patch deployment, as the vulnerability was resolved through version 2.10.2 of Pidgin. Organizations should implement comprehensive patch management procedures to ensure all instances of Pidgin are updated promptly, particularly in environments where multiple users interact through XMPP chat rooms. Network administrators should consider implementing monitoring solutions to detect unusual application crash patterns that might indicate exploitation attempts, while system administrators should review access controls to limit the potential attack surface. The fix implemented by the Pidgin development team involved strengthening input validation within the nickname change function to prevent NULL pointer dereference conditions, demonstrating the importance of robust parameter validation in preventing application-level vulnerabilities. Additionally, organizations should consider implementing application whitelisting policies that restrict execution of unpatched versions of Pidgin until proper updates can be verified and deployed across all systems.