CVE-2011-4601 in Pidgin
Summary
by MITRE
family_feedbag.c in the oscar protocol plugin in libpurple in Pidgin before 2.10.1 does not perform the expected UTF-8 validation on message data, which allows remote attackers to cause a denial of service (application crash) via a crafted (1) AIM or (2) ICQ message associated with buddy-list addition.
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Analysis
by VulDB Data Team • 11/28/2021
The vulnerability described in CVE-2011-4601 represents a critical flaw in the oscar protocol plugin of Pidgin messaging client, specifically within the family_feedbag.c component that handles AIM and ICQ communication protocols. This issue affects Pidgin versions prior to 2.10.1 and demonstrates a classic buffer handling and data validation weakness that can be exploited to disrupt service availability. The vulnerability stems from insufficient UTF-8 validation mechanisms within the message processing pipeline, creating a path for malicious actors to craft specially formatted messages that trigger application instability.
The technical flaw manifests when the oscar protocol plugin receives AIM or ICQ messages that contain malformed UTF-8 sequences during buddy-list addition operations. The family_feedbag.c module fails to properly validate UTF-8 encoding before processing message data, allowing crafted sequences to bypass normal input sanitization. This validation failure creates a condition where malformed data can cause memory corruption or improper state handling within the application's message processing subsystem. When such malicious messages are processed, the application encounters unexpected data structures that lead to memory access violations and subsequent application crashes.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise the stability of communication sessions. Remote attackers can exploit this weakness by sending carefully constructed messages that trigger the validation bypass, causing Pidgin to crash and terminate the messaging session. This disruption affects not only the immediate user experience but also creates potential for more severe consequences when considering that many users rely on Pidgin for business communications or critical messaging infrastructure. The vulnerability is particularly dangerous in environments where continuous availability is required, as it allows attackers to repeatedly disrupt service without requiring authentication or advanced privileges.
Security professionals should note that this vulnerability aligns with CWE-180, which addresses improper input validation, and exhibits characteristics consistent with ATT&CK technique T1499.004 for network denial of service attacks. The flaw represents a classic example of how insufficient data validation in protocol implementations can create exploitable conditions. Organizations should prioritize updating to Pidgin 2.10.1 or later versions where this vulnerability has been addressed through proper UTF-8 validation mechanisms. Additionally, network administrators should consider implementing message filtering at intermediate points to prevent malformed messages from reaching vulnerable clients, though the most effective mitigation remains the application of the official security patch. The vulnerability underscores the importance of proper input validation in protocol implementations and serves as a reminder that even seemingly benign message handling can become a security risk when proper sanitization is omitted.