CVE-2018-10193 in LastPass
Summary
by MITRE
LogMeIn LastPass through 4.9.1 allows remote attackers to cause a denial of service (browser hang) via an HTML document because the resource consumption of onloadwff.js grows with the number of INPUT elements.
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Analysis
by VulDB Data Team • 02/01/2020
The vulnerability identified as CVE-2018-10193 affects LogMeIn LastPass versions through 4.9.1 and represents a significant denial of service weakness that can be exploited remotely by attackers. This issue manifests through malicious HTML documents that trigger excessive resource consumption within the browser environment, specifically targeting the onloadwff.js script which is part of LastPass's browser extension functionality. The flaw demonstrates how web-based security tools can themselves become vectors for attacks when not properly engineered to handle adversarial input patterns.
The technical root cause of this vulnerability lies in the improper handling of HTML document parsing within the LastPass extension's JavaScript execution environment. When the extension encounters an HTML document containing a large number of INPUT elements, the onloadwff.js script experiences exponential resource consumption growth that directly correlates with the quantity of these form elements. This behavior creates a condition where browser performance degrades significantly and eventually leads to complete browser hang or unresponsiveness. The vulnerability operates at the intersection of web browser security and resource management, where the extension's script execution logic fails to implement proper input sanitization or resource limiting mechanisms.
From an operational perspective, this vulnerability presents a substantial risk to end users who may unknowingly encounter malicious HTML documents through phishing campaigns, compromised websites, or social engineering attacks. The attack vector requires minimal technical sophistication from threat actors, as they only need to craft HTML documents with excessive INPUT elements to trigger the denial of service condition. This makes the vulnerability particularly dangerous in enterprise environments where users may interact with untrusted web content regularly. The impact extends beyond individual user experience degradation to potentially disrupting productivity and creating opportunities for more sophisticated attacks that leverage the browser hang condition as a precursor to additional exploitation techniques.
The vulnerability aligns with CWE-400, which addresses "Uncontrolled Resource Consumption," and demonstrates how JavaScript-based browser extensions can become susceptible to resource exhaustion attacks when they fail to implement proper input validation and resource management controls. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to "Network Denial of Service" and potentially to T1566.001 for "Phishing" as the initial delivery mechanism. Organizations should implement immediate mitigations including updating to LastPass versions beyond 4.9.1, implementing web filtering controls to block suspicious HTML content, and educating users about the risks of interacting with untrusted web documents. Additionally, browser security configurations should be reviewed to ensure proper sandboxing and resource limiting for browser extensions, and network monitoring should be enhanced to detect unusual resource consumption patterns that might indicate exploitation attempts.