CVE-2007-5277 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6 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, a different issue than CVE-2006-4560.
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Analysis
by VulDB Data Team • 07/29/2021
The vulnerability described in CVE-2007-5277 represents a significant weakness in Microsoft Internet Explorer 6's DNS resolution behavior that fundamentally undermines network security mechanisms. This flaw operates within the core DNS pinning functionality that IE6 employs to maintain consistent IP address mappings for domains during user sessions. The vulnerability specifically affects how the browser handles DNS pinning when connections fail, creating an exploitable condition that enables sophisticated attack vectors.
The technical implementation of this vulnerability stems from IE6's improper handling of failed TCP connections during DNS pinning operations. When a user visits a website and IE6 establishes a DNS pin for a particular domain on one port such as port 80, the browser continues to use that pinned IP address even when subsequent connection attempts fail on different ports. This behavior creates a window of opportunity for attackers who can exploit the DNS pinning mechanism by crafting malicious URLs that target different TCP ports. The vulnerability is particularly dangerous because it allows attackers to bypass normal security restrictions that would otherwise prevent cross-port access to internal network resources.
The operational impact of this vulnerability is substantial as it enables DNS rebinding attacks, a technique that leverages the browser's DNS caching behavior to circumvent the same-origin policy. Attackers can construct malicious web pages that initially resolve to external IP addresses and then later resolve to internal network addresses, effectively allowing them to access internal systems that would normally be protected from external access. This creates a scenario where remote attackers can potentially gain unauthorized access to internal network resources, including servers and devices that are not directly exposed to the internet. The vulnerability specifically demonstrates the risk when an attacker uses a port 81 URL in an IMG SRC element while the DNS pin had been established for a session on port 80, exploiting the inconsistent handling of failed connections.
From a security standards perspective, this vulnerability aligns with CWE-200, which addresses "Information Exposure," as it provides attackers with information about internal network structures. The behavior also relates to CWE-284, "Improper Access Control," since it allows unauthorized access to network resources through improper handling of connection states. The attack vector described in this CVE maps directly to techniques found in the ATT&CK framework under T1190 "Exploit Public-Facing Application" and T1071.004 "Application Layer Protocol: DNS" where adversaries leverage DNS resolution weaknesses to establish persistent access to network resources.
The mitigation strategies for this vulnerability primarily focus on browser updates and network-level protections. Microsoft addressed this issue through security updates that corrected the DNS pinning behavior in subsequent versions of Internet Explorer. Organizations should implement network segmentation to isolate critical systems from external access and deploy firewall rules that restrict access to internal network resources based on port and protocol. Additionally, implementing DNS server configurations that prevent rapid DNS resolution changes and deploying web application firewalls can help reduce the attack surface. The vulnerability also underscores the importance of keeping browser software current, as this issue was resolved in later versions of Internet Explorer and modern browsers that properly handle DNS pinning and connection failures.