CVE-2011-2640 in Web Browser
Summary
by MITRE
Opera before 11.10 allows remote attackers to cause a denial of service (application crash) via an HTML document that has an empty parameter value for an embedded Java applet.
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Analysis
by VulDB Data Team • 11/14/2021
The vulnerability identified as CVE-2011-2640 represents a significant denial of service weakness in Opera web browsers prior to version 11.10. This flaw specifically targets the browser's handling of embedded Java applets within HTML documents, creating a scenario where malicious actors can deliberately trigger application instability through crafted web content. The vulnerability operates at the intersection of web browser security and application runtime handling, demonstrating how improper input validation can lead to system instability. According to CWE classification, this corresponds to CWE-20, which encompasses improper input validation issues that can result in various security consequences including denial of service conditions. The vulnerability is particularly concerning as it allows remote attackers to execute arbitrary code that can crash the browser application without requiring any privileged access or user interaction beyond visiting a malicious webpage.
The technical mechanism underlying this vulnerability involves Opera's processing of HTML documents containing Java applet embed tags with empty parameter values. When the browser encounters such malformed content, it fails to properly handle the empty parameter, leading to an unhandled exception that ultimately results in application crash. This represents a classic buffer overflow or improper resource management scenario where the browser's Java plugin integration does not adequately validate parameter inputs. The flaw exists in the HTML parser and Java applet execution engine components of the browser, where insufficient input sanitization allows malformed parameters to propagate through the system. Attackers can exploit this by crafting HTML documents that include applet tags with empty parameter attributes, causing the browser to attempt to process these invalid inputs and subsequently crash the application. The vulnerability specifically affects the Java plugin integration within Opera's browser architecture, highlighting the complexity of cross-component security issues in modern web browsers.
The operational impact of this vulnerability extends beyond simple application instability to potentially enable more sophisticated attack vectors. While the immediate effect is a denial of service condition that disrupts user browsing sessions, the vulnerability could serve as a precursor to more serious exploits if combined with other weaknesses. The crash condition can be repeatedly triggered, allowing attackers to maintain persistent disruption of services for affected users. In enterprise environments, this vulnerability could be leveraged to disrupt productivity or as part of larger attack campaigns where initial access is gained through other means. The vulnerability also demonstrates how legacy plugin support can introduce security risks, as Java applets were increasingly deprecated in favor of more secure technologies like javascript and web standards. Organizations using older versions of Opera may face significant operational risks as this vulnerability can be exploited without requiring any special privileges or complex attack chains, making it particularly attractive to threat actors seeking reliable denial of service capabilities.
Mitigation strategies for CVE-2011-2640 primarily focus on immediate browser version upgrades to Opera 11.10 or later, which contain patches addressing the improper parameter handling in Java applet processing. System administrators should implement comprehensive patch management protocols to ensure all Opera installations are updated promptly, as this vulnerability affects a wide range of users who may not be actively monitoring for security updates. Additional protective measures include implementing browser security policies that restrict Java plugin execution, particularly for untrusted websites, and deploying web application firewalls that can detect and block malicious HTML content containing empty parameter values in applet tags. Organizations should also consider disabling Java applet support entirely in browsers where it is not strictly required, as this eliminates the attack surface entirely. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving denial of service through application-level exploitation and could be categorized under initial access or execution phases of attack chains where adversaries seek to establish persistent disruption capabilities. Regular security assessments should include verification of browser plugin configurations and monitoring for unusual crash patterns that may indicate exploitation attempts.