CVE-2005-1618 in Yahoo
Summary
by MITRE
The YMSGR URL handler in Yahoo! Messenger 5.x through 6.0 allows remote attackers to cause a denial of service (disconnect) via a room login or a room join request packet with a third : (colon) and an & (ampersand), which causes Messenger to send a corrupted packet to the server, which triggers a disconnect from the server.
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Analysis
by VulDB Data Team • 07/05/2021
The vulnerability identified as CVE-2005-1618 represents a classic denial of service flaw within the YMSGR URL handler component of Yahoo! Messenger versions 5.x through 6.0. This security weakness specifically targets the protocol handling mechanism that processes room login and room join requests, demonstrating how seemingly minor input validation issues can lead to significant operational disruptions. The flaw operates through a carefully crafted packet structure that exploits the messenger's parsing logic, creating a scenario where legitimate users experience unexpected disconnections from chat rooms and services. From a cybersecurity perspective, this vulnerability exemplifies the importance of robust input sanitization and protocol validation in instant messaging applications that handle real-time network communications.
The technical implementation of this vulnerability involves the manipulation of specific character sequences within the room join request packet structure. Attackers exploit the presence of a third colon character followed by an ampersand to construct malicious packets that the YMSGR handler cannot properly process. This particular sequence triggers a cascading failure within the messenger's packet processing pipeline, where the corrupted packet generation causes the client application to send malformed data to the Yahoo! Messenger server. The server, upon receiving this corrupted packet, responds by terminating the user's connection to the chat room service, effectively performing a denial of service attack against legitimate users who attempt to participate in group communications. This vulnerability operates at the application layer of the network stack, specifically targeting the session management and packet handling components of the messenger protocol implementation.
The operational impact of CVE-2005-1618 extends beyond simple service disruption, as it affects the core functionality of Yahoo Messenger was widely deployed across multiple platforms and user demographics, making it a potentially impactful security flaw that could be exploited at scale. The disruption occurs at the point of service access rather than at a system level, making it particularly insidious as users may not immediately recognize the attack vector or understand why their connections are being terminated.
This vulnerability aligns with several cybersecurity frameworks and classifications, including CWE-129 which addresses improper validation of input boundaries, and CWE-20 which covers input validation issues. The flaw also demonstrates characteristics consistent with ATT&CK technique T1499.002 which involves network denial of service attacks targeting communication protocols. The vulnerability represents a classic case of insufficient input validation where the application fails to properly sanitize user-provided data before processing it within the messaging protocol. From a defensive standpoint, this issue highlights the critical need for implementing comprehensive protocol validation and input sanitization measures in real-time communication applications. Organizations should implement proper packet filtering and validation mechanisms to prevent malformed data from being processed, while also ensuring that applications maintain robust error handling capabilities that prevent single malformed inputs from causing complete service disruptions. The remediation approach should focus on strengthening the URL handler's parsing logic to reject or properly sanitize input containing unexpected character sequences, thereby preventing the cascading failure that leads to the denial of service condition.