CVE-2011-2623 in Web Browser
Summary
by MITRE
Unspecified vulnerability in the SVG BiDi implementation in Opera before 11.50 allows remote attackers to cause a denial of service (application crash or hang) via unknown vectors.
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Analysis
by VulDB Data Team • 11/13/2021
The vulnerability identified as CVE-2011-2623 represents a critical flaw in Opera's handling of Scalable Vector Graphics (SVG) documents, specifically within the BiDi (Bidirectional Text) implementation. This issue affected all versions of the Opera web browser prior to version 11.50, creating a significant security risk that could be exploited by remote attackers to disrupt normal browser operations. The vulnerability resides in the browser's rendering engine's interpretation of SVG files that contain bidirectional text elements, which are commonly used in internationalized web content to properly display text in languages that require different reading directions such as Arabic and Hebrew.
The technical nature of this vulnerability stems from improper memory management and input validation within Opera's SVG processing pipeline. When the browser encounters an SVG document containing specific bidirectional text sequences, the parsing and rendering logic fails to properly handle edge cases in the text directionality algorithms. This malfunction results in memory corruption or infinite loop conditions that cause the browser application to either crash abruptly or become unresponsive, effectively creating a denial of service condition for the affected user. The unspecified nature of the attack vectors suggests that multiple combinations of SVG elements and text properties could trigger the flaw, making it particularly challenging to defend against through simple input filtering approaches.
From an operational perspective, this vulnerability poses significant risks to users who browse the internet regularly, as SVG files are commonly embedded in web pages and can be delivered through various attack vectors including malicious websites, email attachments, or compromised web applications. The remote exploitation capability means that attackers do not need physical access to the target system or special privileges to trigger the vulnerability, making it particularly dangerous in enterprise environments where users may encounter untrusted content. The denial of service impact can range from temporary browser hangs that require manual intervention to complete application crashes that force users to restart their browsing sessions, potentially disrupting productivity and creating opportunities for more sophisticated attacks if attackers can chain this vulnerability with others.
The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and relates to the broader category of input validation failures that can lead to memory corruption issues. From an adversary perspective, this flaw would fit into the attack pattern described by MITRE ATT&CK technique T1203, which involves the use of malicious content to cause system instability or denial of service. Organizations should implement immediate mitigations including mandatory browser updates to Opera 11.50 or later versions, deployment of web application firewalls that can detect and block suspicious SVG content, and user education regarding the risks of visiting untrusted websites. Additionally, security teams should monitor for exploitation attempts through network traffic analysis and implement proper incident response procedures to handle potential service disruption events caused by this vulnerability.