CVE-2011-2641 in Web Browser
Summary
by MITRE
Opera 11.11 allows remote attackers to cause a denial of service (application crash) by setting the FACE attribute of a FONT element within an IFRAME element after changing the SRC attribute of this IFRAME element to an about:blank value.
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Analysis
by VulDB Data Team • 03/23/2025
The vulnerability identified as CVE-2011-2641 represents a denial of service flaw affecting Opera version 11.11 that demonstrates a classic browser memory management issue. This vulnerability specifically targets the browser's handling of HTML elements within iframe contexts, where malicious actors can exploit the interaction between font face attributes and dynamic source changes to trigger application instability. The flaw occurs when an attacker manipulates the FACE attribute of a FONT element nested within an IFRAME element after the iframe's SRC attribute has been programmatically changed to about:blank, which represents a special URI that displays a blank page within the browser context.
The technical mechanism behind this vulnerability stems from Opera's insufficient validation and memory handling when processing nested HTML elements under dynamic content modification scenarios. When the browser encounters the combination of an IFRAME with a modified source to about:blank and a FONT element with a FACE attribute, it fails to properly manage the memory references and rendering contexts, leading to memory corruption or invalid memory access patterns that ultimately result in application crash. This type of vulnerability falls under CWE-125, which describes out-of-bounds read conditions, and CWE-20, which encompasses improper input validation, as the browser does not adequately validate the interaction between these specific HTML attributes and their contextual changes. The vulnerability operates at the intersection of HTML parsing, DOM manipulation, and memory management within the browser's rendering engine, making it particularly challenging to detect and prevent through standard security measures.
The operational impact of this vulnerability extends beyond simple service disruption, as it could potentially be exploited in more sophisticated attack scenarios. While the immediate effect is a denial of service leading to browser application crash, attackers could leverage this flaw to create persistent disruption in web applications or services that rely on Opera 11.11 for functionality. The vulnerability is particularly concerning in environments where users might encounter malicious content through social engineering or compromised websites, as it requires no user interaction beyond visiting a malicious page. From an attacker's perspective, this represents a low-effort, high-impact method for causing service disruption, as demonstrated by the ATT&CK technique T1499.004 for network denial of service attacks. The vulnerability's exploitation does not require elevated privileges or specialized tools, making it accessible to a broad range of threat actors and increasing its potential for widespread impact across various user bases.
Mitigation strategies for this vulnerability primarily focus on browser updates and proper input validation within web applications. The most effective immediate solution involves upgrading to a newer version of Opera that addresses this specific memory management issue, as the vulnerability is resolved in subsequent releases through improved HTML parsing and DOM handling mechanisms. System administrators should implement comprehensive patch management procedures to ensure all Opera installations are updated promptly, as this vulnerability affects the core browser functionality rather than specific web applications. Additionally, web developers should consider implementing content security policies that limit iframe usage and validate all dynamic content modifications to prevent exploitation of similar memory management flaws. Organizations should also deploy web application firewalls and intrusion detection systems that can identify and block malicious HTML constructs targeting this specific vulnerability pattern, though such measures are secondary to the primary mitigation of browser updates and user education regarding safe browsing practices.