CVE-2005-2225 in MSN Messenger
Summary
by MITRE
Microsoft MSN Messenger allows remote attackers to cause a denial of service via a plaintext message containing the ".pif" string, which is interpreted as a malicious file extension and causes users to be kicked from a group conversation. NOTE: it has been reported that Gaim is also affected, so this may be an issue in the protocol or MSN servers.
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Analysis
by VulDB Data Team • 07/24/2017
This vulnerability represents a classic denial of service flaw in Microsoft MSN Messenger that exploits the client-side interpretation of file extensions within chat messages. The vulnerability specifically targets the way MSN Messenger processes plaintext messages containing the ".pif" string, which is interpreted as a malicious file extension by the client software. This particular flaw demonstrates how seemingly innocuous text processing can be weaponized to disrupt legitimate communication channels. The vulnerability operates at the application layer and leverages the trust model inherent in instant messaging protocols where users expect to receive normal chat messages without adverse effects. The issue stems from the client-side validation mechanism that incorrectly treats any occurrence of the ".pif" extension as a potential threat, triggering an automatic disconnection from group conversations.
The technical implementation of this vulnerability involves the manipulation of message content to include the specific string pattern that triggers the malicious file extension interpretation. When a user receives a message containing ".pif" in the plaintext, the MSN Messenger client automatically processes this as a potential file attachment or executable threat, regardless of whether the string appears in the middle of normal conversation text. This behavior violates the principle of least privilege and demonstrates poor input validation in the client-side message parsing logic. The vulnerability is particularly concerning because it operates without requiring any special privileges or authentication, making it easily exploitable by remote attackers who simply need to send a carefully crafted message to a group conversation. The flaw exists in the message interpretation engine that fails to distinguish between legitimate text and maliciously formatted file extension indicators.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader communication reliability issues within MSN Messenger environments. Users participating in group conversations face immediate disconnection from the chat session, effectively preventing them from continuing their communication. This type of denial of service attack can be particularly disruptive in professional or collaborative settings where group communication is essential. The vulnerability affects not only Microsoft's own implementation but also demonstrates protocol-level weaknesses that may impact other clients such as Gaim, indicating a systemic issue within the MSN protocol specification. The attack vector requires minimal technical expertise, making it accessible to a wide range of threat actors who can exploit it to disrupt group communications without sophisticated tools or knowledge.
From a cybersecurity perspective, this vulnerability aligns with CWE-20, which covers "Improper Input Validation," and demonstrates how inadequate validation of user input can lead to unexpected behavior and service disruption. The flaw also relates to ATT&CK technique T1499.004, which involves "Endpoint Denial of Service," where adversaries target client applications to prevent normal operation. The vulnerability's impact is amplified by its ability to affect multiple implementations through shared protocol elements, making it a protocol-level weakness rather than an isolated client-side bug. Mitigation strategies should focus on implementing proper input sanitization and validation at the client-side message processing layer, ensuring that file extension patterns are properly validated against legitimate usage scenarios rather than triggering immediate disconnection responses. The vulnerability highlights the importance of defensive programming practices and the need for robust validation mechanisms in instant messaging applications.
The broader implications of this vulnerability extend to the security architecture of instant messaging systems and demonstrate how protocol-level design decisions can create exploitable weaknesses. The fact that Gaim is also affected suggests that the vulnerability exists in the underlying protocol specification rather than just Microsoft's implementation, indicating a need for protocol-level security hardening. This type of vulnerability represents a common pattern in legacy messaging systems where security considerations were not fully integrated into the original design phases. The issue underscores the critical importance of threat modeling and security testing during the development lifecycle, particularly for applications handling user-generated content in real-time communication environments. Organizations using MSN Messenger or similar protocols should implement network-level filtering to prevent potentially malicious messages from reaching client systems, though this approach provides only partial protection against the vulnerability.