CVE-2003-1135 in Yahoo!
Summary
by MITRE
Buffer overflow in Yahoo! Messenger 5.6 allows remote attackers to cause a denial of service (crash) via a file send request (sendfile) with a large number of "%" (percent) characters after the Yahoo ID.
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Analysis
by VulDB Data Team • 02/05/2025
The vulnerability identified as CVE-2003-1135 represents a classic buffer overflow flaw within Yahoo! Messenger version 5.6 that specifically targets the file transfer functionality of the application. This security weakness arises from insufficient input validation when processing file send requests, particularly those containing excessive percent encoding characters. The flaw exists in the client-side implementation where the application fails to properly sanitize or limit the length of percent characters that can be processed in a file transfer request. When a malicious actor crafts a sendfile request with an excessive number of "%" characters following a Yahoo ID, the application's internal buffer handling mechanism becomes overwhelmed, leading to memory corruption that ultimately results in application crash and denial of service.
From a technical perspective, this vulnerability operates as a stack-based buffer overflow that occurs during the parsing of file transfer requests within the Yahoo! Messenger client. The flaw stems from improper bounds checking in the string processing functions that handle percent-encoded data, which is commonly used in URL encoding and file path specifications. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, where insufficient checks on input data length cause the program to write beyond allocated memory boundaries. The attack vector specifically targets the file send functionality, making it particularly dangerous in environments where file sharing is common and users may be tricked into accepting malicious file transfer requests from untrusted sources.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be exploited to disrupt communication services and potentially serve as a precursor to more sophisticated attacks. When Yahoo Messenger might be used for business communications, as it could be leveraged by attackers to create persistent service disruptions or to mask more serious exploitation attempts. From an attacker's perspective, this vulnerability requires minimal technical expertise to exploit, as it only requires sending a specially crafted file request to a victim's Yahoo! Messenger client. The attack can be executed remotely without requiring authentication or access to the target system, making it a particularly attractive vector for denial of service attacks.
Mitigation strategies for CVE-2003-1135 focus primarily on immediate application updates and input validation improvements. The most effective remediation involves upgrading to a patched version of Yahoo! Messenger that implements proper input sanitization and bounds checking for file transfer requests. Organizations should implement network-level filtering to block suspicious file transfer requests and consider deploying intrusion prevention systems that can detect and block malformed percent-encoded data patterns. Additionally, user education regarding the risks of accepting file transfer requests from untrusted sources becomes critical, as social engineering remains a common attack vector for exploiting such vulnerabilities. The implementation of proper input validation techniques, including length limits and character set restrictions, should be enforced at multiple levels within the application architecture to prevent similar buffer overflow conditions from occurring in other components. This vulnerability also highlights the importance of applying security patches promptly and maintaining up-to-date software versions to protect against known exploits that have been documented in security databases and frameworks such as the MITRE ATT&CK matrix where such vulnerabilities would be categorized under the denial of service technique category.