CVE-2006-5463 in Thunderbird
Summary
by MITRE
Unspecified vulnerability in Mozilla Firefox before 1.5.0.8, Thunderbird before 1.5.0.8, and SeaMonkey before 1.0.6 allows remote attackers to execute arbitrary JavaScript bytecode via unspecified vectors involving modification of a Script object while it is executing.
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Analysis
by VulDB Data Team • 04/27/2026
This vulnerability represents a critical security flaw in the JavaScript engine of Mozilla Firefox Thunderbird and SeaMonkey browsers that existed prior to specific version releases. The issue stems from improper handling of Script objects during execution phases, creating a potential code execution vector that could be exploited by remote attackers. The vulnerability classification aligns with CWE-94, which addresses "Improper Control of Generation of Code" and specifically relates to situations where attacker-controlled data can influence code generation or execution. The flaw occurs when a Script object is modified while actively executing, potentially allowing malicious code to manipulate the execution flow of legitimate JavaScript programs.
The technical mechanism of exploitation involves manipulating Script objects during runtime execution, which creates a race condition or memory corruption scenario. Attackers can craft malicious web content or email messages that modify Script objects while they are in the process of execution, potentially leading to arbitrary code execution within the browser context. This type of vulnerability falls under the ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript" and represents a sophisticated attack vector that leverages the browser's JavaScript engine internals. The vulnerability does not require user interaction beyond visiting a malicious webpage or opening a compromised email message, making it particularly dangerous as it can be exploited automatically.
The operational impact of this vulnerability extends beyond simple code execution to encompass full browser compromise and potential system access. When successfully exploited, attackers could gain the ability to execute arbitrary JavaScript bytecode in the context of the user's browsing session, potentially leading to data theft, system manipulation, or further attack propagation. The vulnerability affects multiple Mozilla products simultaneously, indicating a fundamental flaw in the JavaScript engine shared across these applications. This cross-product impact demonstrates the severity of the underlying issue and the need for coordinated patching across the entire Mozilla ecosystem. The vulnerability could be particularly devastating in enterprise environments where these browsers are widely deployed and users may encounter malicious content through various attack vectors including phishing emails or compromised websites.
Mitigation strategies for this vulnerability include immediate deployment of patched versions of Firefox Thunderbird and SeaMonkey, as well as implementing network-based protections such as web application firewalls that can detect and block malicious JavaScript patterns. Organizations should also consider implementing browser hardening measures including disabling JavaScript in email clients where possible, using security extensions, and maintaining updated threat intelligence feeds to identify potential exploitation attempts. The vulnerability underscores the importance of keeping browser software updated and implementing layered security approaches that can detect and prevent exploitation attempts even when individual defenses may be bypassed. Security teams should also monitor for indicators of compromise related to this vulnerability and ensure that all endpoints are patched promptly to prevent exploitation attempts that could lead to full system compromise.