CVE-2009-3083 in Pidgin
Summary
by MITRE
The msn_slp_sip_recv function in libpurple/protocols/msn/slp.c in the MSN protocol plugin in libpurple in Pidgin before 2.6.2 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via an SLP invite message that lacks certain required fields, as demonstrated by a malformed message from a KMess client.
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Analysis
by VulDB Data Team • 08/22/2021
The vulnerability identified as CVE-2009-3083 represents a critical denial of service flaw within the MSN protocol implementation of Pidgin messaging client. This issue specifically affects the msn_slp_sip_recv function located in libpurple/protocols/msn/slp.c, which handles the reception and processing of Session Initiation Protocol messages within the MSN communication framework. The vulnerability arises from insufficient input validation and error handling mechanisms that fail to properly process malformed SLP invite messages, creating a condition where the application encounters a NULL pointer dereference during message processing.
The technical flaw stems from the function's inability to validate the presence and integrity of required fields within incoming SLP messages before attempting to access them. When a malformed SLP invite message is received from an external source such as the KMess client, the msn_slp_sip_recv function proceeds to dereference pointers that have not been properly initialized or validated, leading to an immediate application crash. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions, and represents a classic example of inadequate error handling in network protocol implementations. The flaw demonstrates poor defensive programming practices where the code assumes the presence of expected message fields without proper verification.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides remote attackers with a reliable method to crash the Pidgin client application. This denial of service condition affects users who are actively communicating through MSN protocol connections, potentially disrupting their messaging sessions and forcing application restarts. The vulnerability is particularly concerning because it can be exploited by any remote attacker who can send SLP messages to a target Pidgin user, making it accessible through various attack vectors including malicious chat participants or compromised accounts. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and represents a common entry point for attackers seeking to disrupt communication services.
Mitigation strategies for this vulnerability involve implementing proper input validation and defensive programming techniques within the affected function. The recommended approach includes adding comprehensive field validation checks before any pointer dereference operations, ensuring that all required SLP message fields are present and properly formatted before processing. Additionally, implementing proper error handling mechanisms that gracefully handle malformed messages rather than allowing the application to crash is essential. The vulnerability was addressed in Pidgin version 2.6.2 through the addition of proper null checks and input validation within the msn_slp_sip_recv function, demonstrating the importance of maintaining robust error handling in protocol implementations. System administrators should prioritize updating to patched versions and consider implementing network-level filtering to prevent malformed SLP messages from reaching vulnerable clients, particularly in environments where Pidgin is used for mission-critical communications.