CVE-2011-2625 in Web Browser
Summary
by MITRE
Opera before 11.50 allows remote attackers to cause a denial of service (application crash) via a SELECT element that contains many OPTION elements.
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Analysis
by VulDB Data Team • 11/13/2021
The vulnerability identified as CVE-2011-2625 represents a classic denial of service flaw affecting Opera web browsers prior to version 11.50. This issue specifically targets the browser's handling of HTML SELECT elements that contain an excessive number of OPTION elements, creating a condition where malicious actors can trigger application instability and crashes. The vulnerability demonstrates how seemingly benign HTML constructs can be exploited to compromise browser stability and availability, highlighting the importance of proper input validation and resource management in web rendering engines.
The technical root cause of this vulnerability lies in Opera's insufficient bounds checking and memory management when processing SELECT elements with excessive OPTION child elements. When the browser encounters a SELECT element containing thousands or tens of thousands of OPTION elements, the rendering engine fails to properly handle the memory allocation and processing requirements, leading to stack overflow conditions or memory exhaustion scenarios. This flaw falls under the category of improper input validation as defined by CWE-20, where the application fails to properly validate or sanitize user-provided HTML content before processing it. The vulnerability represents a specific instance of CWE-122, which deals with insufficient synchronization of data access operations, as the browser's parsing routine does not adequately protect against resource exhaustion during HTML element processing.
The operational impact of CVE-2011-2625 extends beyond simple application crashes, as it can be leveraged as a vector for broader denial of service attacks against Opera users. Attackers can craft malicious web pages containing SELECT elements with excessive OPTION elements, potentially causing browser crashes that disrupt user experience and may be used as part of larger attack campaigns targeting specific user bases. The vulnerability can be particularly effective in environments where Opera is the primary browser or where users may be less likely to update their software regularly. From an attacker perspective, this represents a low-effort, high-impact method for disrupting browser functionality, aligning with ATT&CK technique T1499.100 which focuses on network denial of service attacks through resource exhaustion.
Mitigation strategies for CVE-2011-2625 primarily involve updating to Opera version 11.50 or later, where the parsing routine has been modified to properly handle SELECT elements with excessive OPTION elements. System administrators should implement regular software update policies to ensure users maintain current browser versions that include security patches. Additionally, organizations can deploy web application firewalls or content filtering solutions that can detect and block malicious HTML constructs before they reach user browsers. The vulnerability also underscores the importance of browser sandboxing and memory protection mechanisms, as proper isolation could prevent a single malformed HTML element from causing complete browser crashes. Security teams should monitor for exploitation attempts and consider implementing browser security policies that limit the processing of complex HTML elements, particularly in environments where users may encounter untrusted web content.