CVE-2007-1692 in Windows
Summary
by MITRE
The default configuration of Microsoft Windows uses the Web Proxy Autodiscovery Protocol (WPAD) without static WPAD entries, which might allow remote attackers to intercept web traffic by registering a proxy server using WINS or DNS, then responding to WPAD requests, as demonstrated using Internet Explorer. NOTE: it could be argued that if an attacker already has control over WINS/DNS, then web traffic could already be intercepted by modifying WINS or DNS records, so this would not cross privilege boundaries and would not be a vulnerability. It has also been reported that DHCP is an alternate attack vector.
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Analysis
by VulDB Data Team • 09/14/2018
The vulnerability described in CVE-2007-1692 represents a significant security flaw in Microsoft Windows default configurations that leverages the Web Proxy Autodiscovery Protocol to enable man-in-the-middle attacks. This issue specifically affects systems where Windows automatically discovers proxy settings through WPAD without requiring static entries, creating an attack surface that malicious actors can exploit to intercept and potentially modify web traffic. The vulnerability operates through the automatic discovery mechanism that Windows clients use to locate proxy servers, which can be manipulated by attackers with control over network infrastructure components such as WINS or DNS servers.
The technical implementation of this vulnerability relies on the WPAD protocol's design where Windows clients query for proxy configuration information through DNS or WINS services. When attackers gain control over these services, they can register malicious proxy server entries that will be automatically returned to client systems. This process typically involves the attacker's system responding to WPAD requests with a malicious proxy configuration file, often through a .pac file that instructs the client to route traffic through the attacker's server. The attack is particularly effective when executed through Internet Explorer, which was the primary browser targeted in the original demonstration, though similar vulnerabilities exist in other browsers that support WPAD.
The operational impact of this vulnerability extends beyond simple traffic interception, as it enables sophisticated attack scenarios including credential theft, data exfiltration, and content manipulation. Attackers can leverage this vulnerability to capture authentication credentials, modify web content, or redirect users to malicious sites without detection. The attack vector through DHCP servers adds another layer of complexity as it allows attackers to manipulate proxy settings even when they don't control DNS or WINS infrastructure. This vulnerability directly relates to CWE-284, which addresses improper access control, and aligns with ATT&CK technique T1071.002 for application layer protocol: web protocols, as it involves manipulation of web proxy configurations to intercept traffic. The vulnerability also demonstrates characteristics of privilege escalation through network infrastructure manipulation, as attackers can exploit existing network control to gain unauthorized access to web traffic.
Mitigation strategies for this vulnerability include disabling WPAD functionality when not required, implementing proper DNS security measures such as DNSSEC to prevent unauthorized DNS record modifications, and configuring static proxy settings where possible. Organizations should also consider implementing network monitoring to detect unusual WPAD traffic patterns and ensure that WINS and DNS servers are properly secured with access controls. The recommended approach involves configuring Windows systems to use explicit proxy settings rather than relying on automatic discovery, and implementing network segmentation to limit the scope of potential attacks. Additionally, organizations should regularly audit their network infrastructure for proper access controls and implement security measures that prevent unauthorized modifications to critical network services that could be exploited to manipulate WPAD behavior.