CVE-2007-5276 in Web Browser
Summary
by MITRE
Opera 9 drops DNS pins based on failed connections to irrelevant TCP ports, which makes it easier for remote attackers to conduct DNS rebinding attacks, as demonstrated by a port 81 URL in an IMG SRC, when the DNS pin had been established for a session on port 80.
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Analysis
by VulDB Data Team • 10/31/2017
The vulnerability described in CVE-2007-5276 represents a significant flaw in Opera 9's DNS handling mechanism that directly impacts web browser security and session isolation. This issue stems from the browser's improper management of DNS pinning behavior when connections to specific TCP ports fail, creating exploitable conditions for sophisticated attack vectors. The flaw specifically manifests when Opera drops DNS pins prematurely based on failed connections to irrelevant TCP ports, fundamentally undermining the browser's ability to maintain proper network isolation between different service endpoints. This vulnerability operates at the intersection of network security and web application security, where the improper handling of DNS resolution can be leveraged by malicious actors to bypass security controls that rely on consistent network endpoint identification.
The technical implementation of this vulnerability involves Opera 9's DNS pinning mechanism, which normally maintains a mapping between domain names and IP addresses for the duration of a browsing session to prevent certain types of attacks. When a connection attempt fails to a specific TCP port such as port 81, the browser incorrectly removes the DNS pin that was previously established for a different port like port 80. This behavior creates a window of opportunity for attackers to manipulate DNS resolution through carefully crafted web content, particularly when the malicious content is embedded in an img src attribute referencing a URL on port 81. The vulnerability operates under CWE-200, which addresses information exposure, and more specifically relates to improper handling of network security mechanisms that should maintain consistent endpoint identification throughout a browsing session.
The operational impact of this vulnerability extends beyond simple information disclosure to enable more sophisticated attacks such as DNS rebinding, where an attacker can trick the browser into making requests to internal network resources that would normally be protected by network isolation. When an attacker crafts a malicious URL that references port 81 while the browser has already established a DNS pin for port 80, the browser's premature DNS pin removal allows the attacker to potentially redirect traffic to different IP addresses than originally intended. This creates a dangerous scenario where legitimate network security controls based on port-based isolation can be bypassed, enabling attackers to access internal services or perform actions that should be restricted by the browser's security model. The vulnerability particularly affects scenarios where the same domain is accessed through different ports, as the browser fails to maintain consistent DNS resolution across these different connection points.
This flaw aligns with several ATT&CK techniques including T1071.004 for application layer protocol usage and T1190 for exploitation of remote services, as it enables attackers to manipulate DNS resolution in ways that bypass traditional network security controls. The vulnerability demonstrates how browser security mechanisms can be undermined by seemingly minor implementation details in DNS handling, where the failure to properly maintain DNS pinning consistency creates exploitable conditions. Organizations using Opera 9 would be particularly vulnerable to attacks targeting internal network resources, as the browser's improper DNS handling could allow attackers to circumvent network segmentation controls that rely on consistent port-based access patterns. The impact is particularly severe in environments where internal services are accessible through different ports but should remain isolated from external access, as this vulnerability essentially allows attackers to bridge these security boundaries through clever manipulation of DNS pinning behavior.
The mitigation strategies for this vulnerability require either immediate browser updates to address the DNS pinning implementation flaw or the implementation of additional network-level controls to prevent exploitation of this behavior. Security administrators should consider implementing DNS filtering mechanisms and network segmentation that can detect and prevent the type of DNS rebinding attacks enabled by this vulnerability. Additionally, organizations should ensure that their security monitoring systems are capable of detecting anomalous DNS resolution patterns that might indicate exploitation attempts. The vulnerability serves as a critical reminder of how subtle implementation details in security-critical software can create significant attack surfaces, particularly in browsers where network security controls must be maintained across multiple concurrent connection scenarios. Modern browsers have since addressed similar DNS pinning issues through improved connection handling and more robust DNS resolution management that maintains consistent endpoint identification throughout browsing sessions.