CVE-2018-12571 in Forefront Unified Access Gateway
Summary
by MITRE
uniquesig0/InternalSite/InitParams.aspx in Microsoft Forefront Unified Access Gateway 2010 allows remote attackers to trigger outbound DNS queries for arbitrary hosts via a comma-separated list of URLs in the orig_url parameter, possibly causing a traffic amplification and/or SSRF outcome.
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Analysis
by VulDB Data Team • 04/03/2023
The vulnerability identified as CVE-2018-12571 resides within the uniquesig0/InternalSite/InitParams.aspx component of Microsoft Forefront Unified Access Gateway 2010, representing a significant security flaw that enables remote attackers to manipulate the system's DNS resolution behavior. This issue falls under the category of Server-Side Request Forgery (SSRF) as defined by CWE-918, where the application processes user-supplied input that influences outbound network requests. The vulnerability specifically exploits the orig_url parameter which accepts a comma-separated list of URLs, allowing malicious actors to construct requests that can trigger DNS queries to arbitrary hosts outside the intended network boundaries. The flaw demonstrates characteristics consistent with CWE-444, which addresses HTTP response splitting and related injection vulnerabilities that can lead to traffic amplification effects.
The technical exploitation mechanism involves crafting a malicious request to the vulnerable endpoint with a specially formatted orig_url parameter containing multiple URLs separated by commas. When the system processes this input, it attempts to resolve DNS queries for each URL in the list, potentially causing outbound connections to hosts specified by the attacker. This behavior creates a vector for traffic amplification attacks where a small request can generate disproportionately large responses, while simultaneously enabling SSRF capabilities that can bypass network segmentation and access internal systems. The vulnerability is particularly concerning because it operates at the application layer, potentially allowing attackers to discover internal network topology and access restricted resources that should normally be protected by firewall rules and network segmentation policies.
The operational impact of this vulnerability extends beyond simple DNS enumeration, as it can facilitate more sophisticated attack vectors including internal network reconnaissance, service discovery, and potential access to backend systems that are not directly exposed to the internet. Attackers can leverage this flaw to perform DNS tunneling, exfiltrate data through DNS queries, or use the amplification effect to launch distributed denial-of-service attacks against target systems. The vulnerability's classification under the ATT&CK framework as a DNS Tunneling technique (T1071.004) and Service Hijacking (T1571) demonstrates its potential for both reconnaissance and exploitation phases of an attack lifecycle. Organizations using Microsoft Forefront Unified Access Gateway 2010 are particularly at risk as this appliance typically serves as a gateway for enterprise network access, making it a prime target for attackers seeking to establish persistent access or conduct lateral movement within the network.
Mitigation strategies for CVE-2018-12571 should focus on implementing strict input validation and sanitization of the orig_url parameter to prevent the processing of malicious comma-separated URL lists. Network administrators should consider implementing outbound DNS filtering rules that restrict queries to known good domains and establish proper access controls around the vulnerable endpoint. The implementation of web application firewalls and network segmentation can help reduce the attack surface and limit the potential impact of successful exploitation. Additionally, organizations should ensure that their Microsoft Forefront Unified Access Gateway 2010 appliances are updated with the latest security patches from Microsoft, as this vulnerability was addressed through vendor-provided updates and security releases. The remediation approach should also include monitoring network traffic for unusual DNS query patterns and implementing logging mechanisms to detect potential exploitation attempts. Organizations should conduct regular security assessments to identify similar vulnerabilities in other network appliances and ensure that proper security controls are in place to prevent unauthorized DNS resolution requests that could lead to traffic amplification or internal system access.