CVE-2011-2639 in Web Browser
Summary
by MITRE
Opera before 11.10 does not properly handle hidden animated GIF images, which allows remote attackers to cause a denial of service (CPU consumption) via an image file that triggers continual repaints.
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Analysis
by VulDB Data Team • 11/14/2021
The vulnerability identified as CVE-2011-2639 represents a significant denial of service weakness in Opera web browsers prior to version 11.10. This flaw stems from the browser's inadequate handling of hidden animated gif images, creating a scenario where malicious actors can exploit the rendering engine to consume excessive cpu resources. The vulnerability operates through a specific mechanism involving image processing and repaint operations that occur continuously when such malformed images are encountered during webpage rendering. The issue is particularly concerning because it demonstrates how seemingly benign image formats can be weaponized to disrupt normal browser operations and potentially impact system performance.
The technical implementation of this vulnerability involves the browser's handling of animated gif files that contain hidden or embedded content. When Opera processes these images, it fails to properly manage the animation loop and repaint cycles that occur continuously, leading to a situation where the browser's rendering engine becomes trapped in an infinite loop of visual updates. This behavior causes sustained cpu utilization that can reach extreme levels, effectively exhausting system resources and rendering the browser unresponsive. The flaw specifically affects the browser's image decoding and rendering pipeline, where the handling of hidden animated content does not properly account for the potential for continuous animation cycles.
From an operational perspective, this vulnerability creates substantial risk for users who may encounter maliciously crafted web content or file attachments containing the problematic gif images. The denial of service impact can be severe as it affects the browser's core functionality, potentially requiring users to manually terminate browser processes or restart their systems. The attack vector is particularly insidious because it can be delivered through standard web browsing activities, making it difficult for users to protect themselves without proper updates or security patches. Organizations may face productivity losses and increased support overhead as users experience browser crashes or unresponsiveness, while the vulnerability could also be leveraged as part of larger attack campaigns targeting browser security.
The remediation for this vulnerability requires updating to Opera version 11.10 or later, which includes proper handling of animated gif images and implementation of safeguards against continuous repaint scenarios. Security professionals should prioritize this update as part of their vulnerability management processes, particularly in environments where browser security is critical. Additional mitigations include implementing web content filtering solutions that can identify and block suspicious image content, as well as monitoring browser performance metrics for unusual cpu consumption patterns. This vulnerability aligns with CWE-400, which addresses unchecked resource consumption, and demonstrates characteristics relevant to attack techniques categorized under the denial of service category in the mitre attack framework. Organizations should also consider implementing browser hardening measures and regular security assessments to prevent similar issues from arising in other browser components or third-party plugins.