CVE-2010-5190 in SGOS
Summary
by MITRE
The Active Content Transformation functionality in Blue Coat ProxySG before SGOS 4.3.4.2, 5.x before SGOS 5.4.5.1, 5.5 before SGOS 5.5.4.1, and 6.x before SGOS 6.1.2.1 allows remote attackers to bypass JavaScript detection via HTML entities.
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Analysis
by VulDB Data Team • 05/11/2018
The vulnerability identified as CVE-2010-5190 resides within the Active Content Transformation feature of Blue Coat ProxySG appliances, affecting multiple software versions including SGOS 4.3.4.2 and earlier releases in the 5.x and 6.x branches. This flaw represents a significant security weakness in the content filtering and web proxy capabilities of the appliance, which is designed to protect organizations from malicious web content and enforce security policies across network traffic.
The technical root cause of this vulnerability stems from insufficient validation of HTML entities within the JavaScript detection mechanism. When processing web content, the ProxySG appliance employs Active Content Transformation to analyze and filter potentially harmful code, particularly JavaScript that could be embedded within HTML documents. The flaw occurs because the system fails to properly decode HTML entities before performing JavaScript detection, allowing attackers to encode malicious JavaScript code using HTML entity sequences such as < for < or > for >. This encoding bypasses the security checks that would normally detect and block the execution of dangerous script code.
The operational impact of this vulnerability is severe as it enables remote attackers to circumvent the primary security controls of the ProxySG appliance. An attacker positioned outside the network boundary or within an organization's trusted network can exploit this weakness to inject malicious JavaScript code into web traffic that would otherwise be blocked by the appliance's content filtering rules. This creates a persistent threat vector that can be used to deliver malware, perform cross-site scripting attacks, or establish command and control channels without the organization's security policies being enforced.
The vulnerability aligns with CWE-116, which addresses improper encoding or escaping of output, and represents a classic case of input validation bypass that can be categorized under the ATT&CK technique T1071.004 for application layer protocol traffic. Organizations relying on Blue Coat ProxySG appliances for web security are particularly at risk since the vulnerability affects core functionality that is critical for network protection. The attack surface is broad as it impacts multiple major versions of the software, indicating a fundamental flaw in the implementation rather than a simple patchable issue.
Mitigation strategies should focus on immediate software updates to the patched versions of SGOS 4.3.4.2, 5.4.5.1, 5.5.4.1, and 6.1.2.1, which contain the necessary fixes for proper HTML entity decoding and JavaScript detection. Organizations should also implement additional network monitoring to detect anomalous traffic patterns that might indicate exploitation attempts, and consider deploying complementary security controls such as web application firewalls or advanced threat detection systems to provide defense in depth. Network administrators should review and test their current security policies to ensure that the updated appliance configurations properly enforce content filtering rules without introducing new vulnerabilities.