CVE-2007-1115 in Web Browser
Summary
by MITRE
The child frames in Opera 9 before 9.20 inherit the default charset from the parent window when a charset is not specified in an HTTP Content-Type header or META tag, which allows remote attackers to conduct cross-site scripting (XSS) attacks, as demonstrated using the UTF-7 character set.
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Analysis
by VulDB Data Team • 01/12/2025
The vulnerability described in CVE-2007-1115 represents a critical cross-site scripting flaw in Opera web browser versions prior to 9.20, specifically affecting how child frames handle character encoding inheritance. This issue stems from the browser's improper handling of charset specifications when rendering web content, creating a security gap that malicious actors can exploit to inject and execute arbitrary code within user sessions. The vulnerability manifests when a parent window lacks explicit charset declaration in its HTTP Content-Type header or META tag, causing child frames to inherit the parent's default charset setting.
The technical flaw occurs at the browser rendering engine level where Opera's implementation fails to properly isolate character encoding contexts between parent and child frames. When a parent window operates with a default charset such as UTF-7, child frames automatically inherit this setting even when they should maintain their own independent charset handling. This inheritance behavior creates a dangerous scenario where malicious content loaded into child frames can exploit the inherited encoding to bypass security mechanisms. The UTF-7 character set becomes particularly dangerous because it allows attackers to encode malicious JavaScript code in a way that appears benign to traditional security filters while still executing when interpreted by the browser.
The operational impact of this vulnerability extends beyond simple XSS attacks, as it provides attackers with a sophisticated method to circumvent standard security measures that rely on proper charset handling. Attackers can craft malicious content that appears to be legitimate text when viewed through the inherited UTF-7 encoding, making detection significantly more difficult. This vulnerability aligns with CWE-1004 which addresses insecure default conditions, and represents a classic case of improper input validation where the browser fails to properly validate or isolate character encoding contexts between different document frames. The attack vector specifically enables persistent cross-site scripting where malicious scripts can be executed in the context of a user's session, potentially leading to session hijacking, data theft, or further exploitation of the victim's browser environment.
This vulnerability demonstrates the critical importance of proper character encoding isolation in web browser implementations and aligns with ATT&CK technique T1211 which covers exploitation for defense evasion through encoding techniques. The flaw essentially creates a pathway for attackers to bypass security controls that depend on proper encoding detection and handling, making it particularly dangerous in environments where users may encounter untrusted web content. Security professionals should note that this vulnerability highlights the need for comprehensive testing of browser behavior regarding character encoding inheritance, particularly in complex web applications that utilize multiple frames or iframes. The vulnerability also underscores the importance of maintaining up-to-date browser versions and implementing proper content security policies to mitigate the risk of exploitation through such encoding-based attacks.
The remediation approach for this vulnerability requires immediate browser updates to Opera 9.20 or later versions where the charset inheritance behavior has been properly addressed. Organizations should also implement comprehensive web application security measures including proper content security policies, input validation, and regular security assessments to prevent exploitation of similar encoding-based vulnerabilities. Additionally, this vulnerability emphasizes the need for browser vendors to maintain rigorous testing procedures for character encoding handling and to implement proper isolation mechanisms between different document contexts to prevent cross-context security issues.