CVE-2015-6166 in Silverlight
Summary
by MITRE
Microsoft Silverlight 5 before 5.1.41105.00 allows remote attackers to execute arbitrary code or cause a denial of service (out-of-bounds read or write access) via unspecified open and close requests, aka "Microsoft Silverlight RCE Vulnerability."
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Analysis
by VulDB Data Team • 06/29/2022
Microsoft Silverlight 5 before version 5.1.41105.00 contains a critical vulnerability that enables remote attackers to execute arbitrary code or cause denial of service through unspecified open and close requests. This vulnerability falls under the category of out-of-bounds read or write access flaws, which represent a significant security risk in client-side applications. The vulnerability affects the Silverlight runtime environment that was widely used for delivering rich internet applications and multimedia content across various operating systems including windows vista, windows 7, windows 8, and windows server 2008 r2. The flaw exists in the handling of open and close requests within the silverlight runtime, specifically when processing certain data structures or memory operations. This type of vulnerability is particularly dangerous because it can be exploited remotely without requiring any user interaction or authentication, making it an attractive target for attackers seeking to compromise systems running affected silverlight versions.
The technical nature of this vulnerability stems from improper bounds checking within the silverlight runtime's request handling mechanisms. When the application processes open and close requests, it fails to adequately validate input parameters or memory boundaries, leading to potential buffer overflows or underflows. This allows attackers to manipulate memory locations and execute malicious code with the privileges of the silverlight application. The out-of-bounds read or write access capabilities provide attackers with multiple exploitation vectors, enabling them to either gain code execution privileges or cause the application to crash through denial of service attacks. This vulnerability is particularly concerning as it affects a widely deployed technology that was commonly used in enterprise environments, educational institutions, and consumer applications, making the potential attack surface extremely broad.
The operational impact of this vulnerability extends beyond simple code execution, as it can lead to complete system compromise when combined with other exploitation techniques. Attackers can leverage this vulnerability to install malware, steal sensitive data, or establish persistent access to compromised systems. The fact that this vulnerability affects the silverlight runtime means that any application or website utilizing silverlight technology could become a vector for exploitation. Organizations running affected versions of silverlight are at risk of being targeted by sophisticated attackers who may use this vulnerability as part of broader attack campaigns. The vulnerability also represents a significant challenge for security teams because silverlight applications are often embedded within web pages and may be difficult to monitor or control centrally. The impact is further compounded by the fact that many organizations may not be aware of all silverlight applications running on their networks, creating blind spots in security monitoring and incident response.
Mitigation strategies for this vulnerability should include immediate patching of all affected silverlight installations to version 5.1.41105.00 or later, which contains the necessary security fixes. Organizations should conduct comprehensive inventory audits to identify all systems running affected silverlight versions and prioritize remediation efforts accordingly. Network segmentation and access controls should be implemented to limit exposure of silverlight applications to untrusted networks. Security monitoring should be enhanced to detect unusual patterns in silverlight application behavior or memory access violations. Additionally, organizations should consider migrating away from silverlight technology altogether, as microsoft has officially discontinued support for silverlight and the technology is no longer recommended for use. The vulnerability aligns with common attack patterns documented in the attack tree framework, particularly those involving client-side exploitation and privilege escalation techniques. From a cwes perspective, this vulnerability relates to multiple categories including cwe-125 out-of-bounds read and cwe-787 out-of-bounds write, both of which are classified as high severity flaws in the common weakness enumeration system. Organizations should also consider implementing application whitelisting policies and restricting execution of silverlight applications to trusted environments only, as part of their broader defense-in-depth strategy against similar vulnerabilities.