CVE-2011-2943 in Pidgin
Summary
by MITRE
The irc_msg_who function in msgs.c in the IRC protocol plugin in libpurple 2.8.0 through 2.9.0 in Pidgin before 2.10.0 does not properly validate characters in nicknames, which allows user-assisted remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted nickname that is not properly handled in a WHO response.
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Analysis
by VulDB Data Team • 03/19/2021
The vulnerability identified as CVE-2011-2943 represents a critical denial of service flaw within the IRC protocol implementation of Pidgin messaging client. This issue affects libpurple versions 2.8.0 through 2.9.0, which were part of Pidgin releases prior to version 2.10.0. The vulnerability stems from improper validation of nickname characters within the irc_msg_who function located in the msgs.c file of the IRC protocol plugin. The flaw manifests when processing WHO responses from IRC servers, where maliciously crafted nicknames can trigger unexpected behavior in the client application.
The technical exploitation of this vulnerability occurs through a NULL pointer dereference condition that results in application crash. When the irc_msg_who function processes a WHO response containing specially crafted nickname characters, the validation logic fails to properly sanitize or handle these inputs. This failure leads to the dereferencing of a null pointer, causing the application to terminate abruptly and resulting in a denial of service condition for legitimate users. The vulnerability specifically targets the IRC protocol plugin within libpurple, which serves as the core messaging library for Pidgin and other applications supporting multiple instant messaging protocols.
From an operational perspective, this vulnerability creates significant risk for users who rely on Pidgin for IRC communication. Attackers can remotely trigger service disruption by sending specially crafted WHO responses containing malformed nicknames, effectively causing legitimate users to lose connectivity or experience application crashes. The user-assisted nature of this vulnerability means that the attack requires some level of interaction from the victim, typically through joining a malicious IRC channel or receiving messages from compromised users. This makes the vulnerability particularly dangerous in collaborative environments where users may encounter untrusted content from network peers.
The vulnerability aligns with CWE-125, which addresses out-of-bounds read conditions, and more specifically with CWE-476, which covers NULL pointer dereference issues. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and potentially T1059.001 for command and scripting interpreter usage in crafting the malicious nickname payloads. The impact extends beyond simple service disruption as it can also affect user experience and potentially enable more sophisticated attacks if combined with other vulnerabilities. Organizations using Pidgin for IRC communications should prioritize patching to address this vulnerability, as the fix in Pidgin 2.10.0 properly validates nickname characters and prevents the NULL pointer dereference condition.