CVE-2005-1671 in Yahoo
Summary
by MITRE
The Logfile feature in Yahoo! Messenger 5.x through 6.0 can be activated by a YMSGR: URL and writes all output to a single ypager.log file, even when there are multiple users, and does not properly warn later users that the feature has been enabled, which allows local users to obtain sensitive information from other users.
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Analysis
by VulDB Data Team • 07/09/2018
The vulnerability described in CVE-2005-1671 represents a significant security flaw in Yahoo! Messenger versions 5.x through 6.0 that stems from improper handling of the logfile feature within the application. This issue manifests when a YMSGR: URL is processed by the messenger client, which triggers the activation of logging functionality that writes all communication output to a single shared file named ypager.log. The flaw lies in the application's failure to implement proper access controls or user isolation mechanisms when multiple users interact with the same system, creating a scenario where sensitive information from different user sessions becomes accessible to unauthorized parties.
The technical implementation of this vulnerability involves the lack of proper file access controls and user context management within the Yahoo! Messenger application. When multiple users operate on the same system, the logging mechanism does not distinguish between different user sessions or implement appropriate file permissions that would prevent cross-contamination of sensitive data. The system fails to warn subsequent users that the logging feature has already been enabled, creating a situation where new users are unaware that their communications might be visible to others who previously used the application. This design flaw directly violates fundamental security principles of information isolation and access control, allowing local privilege escalation through data exposure rather than traditional authentication bypass techniques.
The operational impact of this vulnerability extends beyond simple information disclosure to encompass potential compromise of user privacy and communication confidentiality. Local users can gain access to sensitive information from other users' conversations, chat logs, and potentially personal data that was not intended for public viewing. This vulnerability particularly affects multi-user systems where different individuals share the same computing environment, such as internet cafes, shared workstations, or home networks with multiple family members using the same computer. The exposure of such information could lead to identity theft, social engineering attacks, or other malicious activities that exploit the disclosed communication patterns and personal details.
This vulnerability can be categorized under CWE-200 (Information Exposure) and CWE-284 (Improper Access Control) within the Common Weakness Enumeration framework, representing a clear violation of the principle of least privilege and proper resource isolation. From an ATT&CK framework perspective, this issue maps to T1005 (Data from Local System) and T1083 (File and Directory Discovery) as attackers can leverage this weakness to discover and access sensitive files containing other users' communication data. The vulnerability also demonstrates characteristics of T1566 (Phishing) in that it can be exploited through URL-based attack vectors that trick users into activating the logging feature. Mitigation strategies should focus on implementing proper file access controls, user session isolation, and ensuring that logging features properly warn users about existing logging activities. System administrators should consider disabling the problematic logging feature entirely or implementing additional access controls to prevent unauthorized file access, while users should be educated about the risks of clicking untrusted YMSGR URLs that could trigger this vulnerability.