CVE-2005-2871 in Firefox
Summary
by MITRE
Buffer overflow in the International Domain Name (IDN) support in Mozilla Firefox 1.0.6 and earlier, and Netscape 8.0.3.3 and 7.2, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a hostname with all "soft" hyphens (character 0xAD), which is not properly handled by the NormalizeIDN call in nsStandardURL::BuildNormalizedSpec.
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Analysis
by VulDB Data Team • 12/26/2024
This vulnerability represents a critical buffer overflow flaw in the International Domain Name handling mechanisms of major web browsers including Mozilla Firefox versions 1.0.6 and earlier, as well as Netscape 8.0.3.3 and 7.2. The issue stems from inadequate processing of Unicode characters, specifically soft hyphens represented by character 0xAD, within the NormalizeIDN function located in the nsStandardURL::BuildNormalizedSpec method. The vulnerability falls under the CWE-121 buffer overflow category, where insufficient bounds checking allows malicious input to overwrite adjacent memory locations.
The technical execution of this vulnerability occurs when a remote attacker crafts a hostname containing exclusively soft hyphens, which the affected browsers fail to properly normalize during URL processing. This improper handling causes the application to allocate insufficient buffer space for the normalized domain name, leading to memory corruption when the system attempts to process the malformed input. The flaw manifests as an immediate crash of the browser process, resulting in a denial of service condition that prevents legitimate users from accessing web resources. However, the vulnerability presents a potential for more severe exploitation as memory corruption can theoretically be leveraged to execute arbitrary code with the privileges of the affected browser process.
From an operational perspective, this vulnerability creates significant risks for users who may inadvertently encounter maliciously crafted URLs in web content, email attachments, or other network communications. The attack vector requires no special privileges from the attacker, making it particularly dangerous as it can be exploited through simple web page loading or navigation to maliciously constructed domains. The impact extends beyond simple service disruption to potential system compromise, as demonstrated by similar buffer overflow vulnerabilities in web browser components that have been exploited for remote code execution in the past. This vulnerability demonstrates the inherent complexity of Unicode processing in web applications and the critical importance of proper input validation and bounds checking.
Mitigation strategies for this vulnerability include immediate deployment of security patches provided by the browser vendors, which typically involve implementing proper bounds checking in the IDN normalization routines and updating the Unicode handling logic to correctly process soft hyphens. Organizations should also implement network-level protections such as URL filtering and content inspection systems that can detect and block URLs containing suspicious Unicode sequences. Additionally, users should be educated about the risks of visiting untrusted websites and the importance of keeping browser software updated. The vulnerability highlights the need for comprehensive testing of internationalization features and adherence to security standards such as those outlined in the OWASP Top Ten and NIST guidelines for secure coding practices in web applications. This particular flaw exemplifies how seemingly benign Unicode characters can create serious security implications when not properly handled in application code, emphasizing the importance of robust input validation and memory safety practices in software development.