CVE-2009-1889 in Pidgin
Summary
by MITRE
The OSCAR protocol implementation in Pidgin before 2.5.8 misinterprets the ICQWebMessage message type as the ICQSMS message type, which allows remote attackers to cause a denial of service (application crash) via a crafted ICQ web message that triggers allocation of a large amount of memory.
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Analysis
by VulDB Data Team • 04/09/2025
The vulnerability identified as CVE-2009-1889 represents a critical flaw in the OSCAR protocol implementation within Pidgin messaging client versions prior to 2.5.8. This issue stems from improper message type handling where the application incorrectly interprets ICQWebMessage as ICQSMS message type, creating a fundamental misclassification that can be exploited by remote attackers. The flaw exists within the protocol parsing logic that processes incoming ICQ messages, specifically affecting how the software handles different message categories within the OSCAR framework. The OSCAR protocol serves as the foundation for ICQ messaging services and is widely implemented across various instant messaging clients, making this vulnerability particularly concerning for widespread impact.
The technical nature of this vulnerability manifests through a memory allocation error that occurs when processing crafted ICQ web messages. When an attacker sends a specially crafted message that should be classified as ICQWebMessage, the flawed implementation erroneously treats it as ICQSMS, which triggers different processing paths within the application. This misinterpretation leads to improper memory allocation calculations, where the application attempts to allocate an excessive amount of memory resources based on malformed message parameters. The vulnerability is classified as a buffer overflow condition under CWE-121, specifically involving heap-based buffer overflows that occur due to improper input validation and type handling. The memory allocation process becomes corrupted when the application attempts to process the malformed message, leading to unpredictable behavior and eventual application termination.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a potential vector for more sophisticated attacks within the broader context of the MITRE ATT&CK framework. While the immediate effect is application crash and service disruption, the underlying memory handling flaw could potentially be exploited for more advanced techniques such as memory corruption attacks or privilege escalation depending on the execution environment. The vulnerability affects users of Pidgin who are connected to ICQ networks, making it particularly relevant in enterprise environments where instant messaging systems are widely deployed. Attackers can leverage this vulnerability through simple network-based attacks without requiring authentication or elevated privileges, making it an attractive target for malicious actors seeking to disrupt communications services. The vulnerability's exploitation requires minimal technical expertise, as it only requires sending a malformed message to a target user's client.
Mitigation strategies for this vulnerability primarily focus on immediate software updates and patches, with the most effective solution being the upgrade to Pidgin version 2.5.8 or later where the message type handling has been corrected. Organizations should implement network monitoring to detect unusual message patterns that might indicate exploitation attempts, particularly focusing on ICQ protocol traffic analysis. The fix implemented by the Pidgin development team addresses the core issue by adding proper type validation and ensuring that ICQWebMessage and ICQSMS messages are correctly classified before processing. Network administrators should also consider implementing message filtering rules that can identify and block suspicious ICQ messages, particularly those with malformed headers or unexpected parameter values. Additionally, organizations should conduct regular security assessments of their instant messaging infrastructure to identify similar vulnerabilities in other protocol implementations, as this type of message type confusion vulnerability can occur in various communication protocols and applications.