CVE-2011-1091 in Pidgin
Summary
by MITRE
libymsg.c in the Yahoo! protocol plugin in libpurple in Pidgin 2.6.0 through 2.7.10 allows (1) remote authenticated users to cause a denial of service (NULL pointer dereference and application crash) via a malformed YMSG notification packet, and allows (2) remote Yahoo! servers to cause a denial of service (NULL pointer dereference and application crash) via a malformed YMSG SMS message.
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Analysis
by VulDB Data Team • 10/19/2021
The vulnerability described in CVE-2011-1091 represents a critical denial of service flaw within the Yahoo protocol plugin, which serves as the communication interface for Yahoo! messaging services within the Pidgin client environment.
The technical implementation of this vulnerability involves the failure to properly validate incoming YMSG protocol data structures during packet processing. When the libymsg.c component receives malformed notification packets or SMS messages from Yahoo! servers, it attempts to access memory locations that have not been properly initialized or allocated, resulting in null pointer dereference exceptions. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. The error occurs during the parsing phase of YMSG protocol communication where the application assumes certain data structures will contain valid references when they may actually be null, leading to abrupt program termination.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise user communication reliability and system stability. Remote authenticated users who can establish connections to the Yahoo servers to exploit the same flaw, meaning that any user connected to Yahoo! services through Pidgin could be affected regardless of their authentication status. This makes the vulnerability particularly dangerous as it can be exploited without requiring specific credentials beyond basic account access. The crash conditions result in complete application termination, forcing users to restart Pidgin and potentially lose unsaved chat sessions or connection state information.
From a cybersecurity perspective, this vulnerability demonstrates the importance of proper input validation and error handling in protocol implementations. The ATT&CK framework categorizes this as a Denial of Service technique through application level flaws, specifically targeting software reliability and stability. The vulnerability represents a classic example of insufficient boundary checking and memory management in network protocol handlers. Organizations using Pidgin for communication should immediately implement mitigations including updating to patched versions of the software, implementing network level filtering to prevent malformed packets, or disabling the Yahoo! protocol plugin until proper patches are applied. The vulnerability also highlights the need for robust testing procedures including fuzzing and protocol stress testing to identify similar memory corruption issues in messaging and communication applications. Security teams should monitor for exploitation attempts and ensure that all communication clients are regularly updated to address known vulnerabilities in third-party libraries and protocols.