CVE-2003-0106 in Enterprise Firewall
Summary
by MITRE
The HTTP proxy for Symantec Enterprise Firewall (SEF) 7.0 allows proxy users to bypass pattern matching for blocked URLs via requests that are URL-encoded with escapes, Unicode, or UTF-8.
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Analysis
by VulDB Data Team • 01/11/2019
The vulnerability identified as CVE-2003-0106 affects the Symantec Enterprise Firewall version 7.0 HTTP proxy component, representing a significant security flaw in network traffic filtering mechanisms. This issue stems from inadequate input validation within the proxy's URL pattern matching system, which fails to properly decode and analyze URL-encoded requests before determining whether they should be blocked or allowed. The flaw specifically targets the proxy's ability to detect and prevent access to malicious or restricted web resources through various encoding techniques that are commonly used to evade security controls.
The technical implementation of this vulnerability exploits the difference between how the proxy processes incoming requests and how it applies its filtering rules. When users submit URL-encoded requests containing blocked content, the proxy's pattern matching system does not adequately normalize or decode these encoded sequences before performing its security checks. This allows attackers to craft requests using URL encoding, Unicode escapes, or UTF-8 encoding to bypass the firewall's content filtering mechanisms. The vulnerability essentially creates a bypass path where malicious content can be accessed despite being explicitly blocked by the firewall's ruleset, as the proxy fails to recognize that the encoded content matches the patterns it is designed to prevent.
From an operational impact perspective, this vulnerability significantly undermines the security posture of organizations relying on Symantec Enterprise Firewall 7.0 for network protection. The ability to bypass URL filtering means that malicious websites, phishing pages, or unauthorized content can be accessed without detection, potentially leading to data breaches, malware infections, or unauthorized access to sensitive resources. This flaw particularly affects organizations that depend on the proxy for content filtering and web access control, as it essentially renders portions of their security policy ineffective. The vulnerability could be exploited by both internal malicious actors and external threat groups seeking to gain unauthorized access to restricted resources or to deliver malicious payloads through bypassed web traffic.
Security professionals should note that this vulnerability aligns with CWE-180, which describes the issue of insufficient input validation or normalization in security filtering systems. The flaw also demonstrates characteristics consistent with techniques documented in the MITRE ATT&CK framework under the T1071.004 tactic for application layer protocol usage and T1566 for social engineering through phishing. Organizations should implement immediate mitigations including applying the vendor-provided patches, implementing additional monitoring for unusual URL-encoded traffic patterns, and considering alternative security controls for web filtering. The vulnerability highlights the critical importance of proper input normalization and validation in security appliances, particularly those handling network traffic filtering where bypass opportunities can have severe consequences for organizational security.