CVE-2007-5540 in Web Browser
Summary
by MITRE
Unspecified vulnerability in Opera before 9.24 allows remote attackers to overwrite functions on pages from other domains and bypass the same-origin policy via unknown vectors.
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Analysis
by VulDB Data Team • 06/02/2025
The vulnerability identified as CVE-2007-5540 represents a critical security flaw in Opera web browsers prior to version 9.24 that fundamentally undermines the browser's core security model. This issue falls under the category of cross-site scripting and privilege escalation vulnerabilities, specifically targeting the same-origin policy enforcement mechanisms that are essential for web security. The vulnerability enables remote attackers to manipulate function objects across different domains, effectively breaking the isolation boundaries that separate web content from different origins. This type of flaw directly violates fundamental web security principles and creates a pathway for malicious actors to execute unauthorized code across domain boundaries. The same-origin policy serves as the cornerstone of web security by preventing scripts from one origin from accessing resources or functions belonging to another origin, and this vulnerability essentially creates a backdoor that bypasses these protections.
The technical implementation of this vulnerability appears to involve improper handling of function objects within the browser's JavaScript engine, allowing attackers to inject malicious code that can overwrite or manipulate function definitions across different security contexts. This flaw likely stems from insufficient validation mechanisms when processing cross-domain requests or when managing the execution environment of JavaScript functions. The vulnerability's classification aligns with CWE-20, which addresses improper input validation, and specifically relates to CWE-94, which deals with the execution of arbitrary code through improper handling of dynamic code generation. Attackers could exploit this weakness by crafting malicious web pages that leverage the function overwriting capability to execute code in the context of other domains, potentially accessing sensitive data or performing unauthorized actions on behalf of users.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it provides attackers with the ability to perform sophisticated attacks against users of affected Opera versions. Users could be subjected to session hijacking, data theft, or malicious redirection attacks when visiting compromised websites or when exposed to cross-site scripting payloads. The vulnerability's remote exploitation capability means that attackers do not need physical access to the target system or any special privileges to exploit it. This creates a significant risk for enterprise environments where users may inadvertently visit malicious websites, leading to potential data breaches or system compromises. The attack surface is particularly concerning because it affects the browser's fundamental security architecture, making it difficult for users to detect or prevent such attacks without proper browser updates.
Organizations and individuals should prioritize immediate remediation by upgrading to Opera version 9.24 or later, which includes patches addressing this vulnerability. Security teams should implement network monitoring to detect potential exploitation attempts and consider deploying web application firewalls or content filtering solutions as additional defensive measures. The vulnerability demonstrates the importance of maintaining up-to-date browser software and highlights the need for regular security assessments of web applications. From a threat modeling perspective, this vulnerability maps to ATT&CK technique T1059.007 for script execution and T1566 for social engineering, as attackers may use this weakness to deliver malicious payloads through compromised websites. Organizations should also consider implementing browser hardening measures and educating users about the risks of visiting untrusted websites to reduce the likelihood of successful exploitation attempts.