CVE-2008-3435 in Browser Toolbar
Summary
by MITRE
LinkedIn Browser Toolbar 3.0.3.1100 and earlier does not properly verify the authenticity of updates, which allows man-in-the-middle attackers to execute arbitrary code via a Trojan horse update, as demonstrated by evilgrade and DNS cache poisoning.
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Analysis
by VulDB Data Team • 11/21/2017
The vulnerability identified as CVE-2008-3435 affects the LinkedIn Browser Toolbar version 3.0.3.1100 and earlier, representing a critical security flaw in the software update mechanism. This issue stems from inadequate verification processes that fail to authenticate the legitimacy of software updates, creating a significant attack surface for malicious actors. The vulnerability specifically targets the toolbar's update system, which is designed to automatically download and install new versions of the browser extension. When users attempt to update the toolbar, the system does not properly validate the digital signatures or cryptographic hashes of the update files, leaving the installation process susceptible to tampering. This weakness enables attackers to exploit the update mechanism as a vector for code execution, fundamentally compromising the security posture of affected systems.
The technical exploitation of this vulnerability involves man-in-the-middle attack techniques where adversaries intercept the update communication between the toolbar and its update servers. Attackers can employ methods such as evilgrade or DNS cache poisoning to manipulate the update process, replacing legitimate update files with malicious payloads that are indistinguishable from authentic updates to the user. The vulnerability operates at the intersection of software integrity verification and network security, creating a scenario where the very mechanism designed to protect users becomes a vector for compromise. The flaw essentially removes the cryptographic verification checks that should ensure update authenticity, allowing attackers to inject arbitrary code that executes with the privileges of the toolbar installation process. This type of vulnerability is classified under CWE-310 as "Cryptographic Issues" and specifically relates to the absence of proper validation mechanisms for update authenticity.
The operational impact of CVE-2008-3435 extends beyond simple code execution, as it represents a fundamental breakdown in the security model of the browser toolbar. When successfully exploited, attackers can gain persistent access to user systems through the toolbar's elevated privileges, potentially leading to data exfiltration, credential theft, or further network compromise. The vulnerability affects users who rely on the toolbar for LinkedIn integration within their web browsers, creating a widespread attack surface across numerous endpoints. The exploitation techniques align with ATT&CK tactics such as T1195 for content injection and T1059 for execution through legitimate system processes, making this vulnerability particularly dangerous in enterprise environments where browser toolbars are commonly deployed. The persistence mechanism provided by the toolbar installation allows attackers to maintain access even after system reboots, creating a long-term security risk.
Mitigation strategies for this vulnerability require immediate action to address the root cause of the update verification failure. Organizations should implement immediate patching of the LinkedIn Browser Toolbar to versions that properly validate update authenticity, typically through cryptographic signature verification. Network administrators should consider implementing DNS filtering mechanisms and monitoring for suspicious update traffic to detect potential exploitation attempts. The remediation process should also include user education about the risks of unauthorized software updates and the importance of verifying update sources. Security controls should be implemented to prevent man-in-the-middle attacks through network segmentation and traffic monitoring, as the vulnerability is fundamentally rooted in network-level attack vectors. Additionally, organizations should consider implementing application whitelisting policies that restrict the execution of browser toolbars to known good versions only, reducing the attack surface for similar vulnerabilities in the future. The remediation approach must address both the immediate exploitation risk and the underlying architectural weakness in the update verification system.