CVE-2010-0423 in Pidgin
Summary
by MITRE
gtkimhtml.c in Pidgin before 2.6.6 allows remote attackers to cause a denial of service (CPU consumption and application hang) by sending many smileys in a (1) IM or (2) chat.
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Analysis
by VulDB Data Team • 05/01/2026
The vulnerability identified as CVE-2010-0423 represents a significant denial of service weakness within the Pidgin instant messaging client software. This flaw exists in the gtkimhtml.c component which handles HTML rendering for instant messages and chat conversations. The vulnerability specifically affects Pidgin versions prior to 2.6.6, making it a critical issue for users running outdated software. The flaw operates through a straightforward yet effective mechanism that exploits the application's handling of smiley characters within message content.
The technical implementation of this vulnerability stems from inadequate input validation and processing within the HTML rendering engine of Pidgin's user interface. When a remote attacker sends a message containing an excessive number of smiley characters, the gtkimhtml.c module enters an inefficient processing loop that consumes disproportionate CPU resources. This occurs because the application fails to implement proper bounds checking or rate limiting for smiley character processing, causing the HTML parser to repeatedly iterate through the malformed input. The vulnerability manifests as either complete application hanging or severe CPU consumption that renders the messaging client unusable for legitimate users. The flaw affects both instant messaging and chat room scenarios, making it particularly dangerous in multi-user environments where attackers can easily exploit the vulnerability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of communication channels for legitimate users. In enterprise environments where Pidgin serves as a primary communication tool, this vulnerability could enable attackers to disrupt business communications and collaboration. The resource exhaustion effect means that even a single malicious message could cause the application to become unresponsive for extended periods, potentially affecting multiple users if the attacker targets shared chat rooms or sends messages to numerous contacts. This type of vulnerability aligns with CWE-400, which categorizes unchecked resource allocation as a fundamental weakness in software design. The attack vector requires minimal sophistication and can be executed through simple message transmission, making it particularly dangerous for widespread exploitation.
Mitigation strategies for CVE-2010-0423 should prioritize immediate software updates to Pidgin version 2.6.6 or later, which contain the necessary patches to address the excessive smiley processing behavior. System administrators should implement network-level filtering to limit the frequency of smiley character processing and consider implementing message size limits to prevent abuse. The vulnerability demonstrates the importance of proper input sanitization and resource management in user interface components, particularly those involved in HTML rendering. Organizations should also consider implementing monitoring solutions to detect unusual CPU consumption patterns that might indicate exploitation attempts. This vulnerability exemplifies ATT&CK technique T1499.001, which involves resource exhaustion through malicious input processing, and highlights the need for robust defensive measures in messaging applications. The incident underscores the critical importance of regular security updates and proper input validation in preventing denial of service attacks that leverage seemingly benign user interface features.