CVE-2013-0074: Microsoft Silverlight Double Dereference Vulnerability

CVE-2013-0074 is a remote code execution vulnerability in Microsoft Silverlight. The product fails to properly validate pointers while rendering HTML objects, so a crafted Silverlight application can be used by an attacker to run code on the affected system. Because the vulnerability has been associated with ransomware activity and the product itself is end-of-life, any remaining installations represent ongoing risk that defenders should treat as high priority.

Organizations that still host or allow Silverlight content need to confirm exposure, remove the component where possible, and apply compensating controls until it is fully eliminated. Specifics such as exact build numbers or patch identifiers must be confirmed against the original vendor advisory.

How it works

The vulnerability is described as a double-dereference flaw. During HTML object rendering, Silverlight does not adequately validate certain pointers before using them. An attacker who can deliver a malicious Silverlight application can trigger the improper pointer handling, leading to memory corruption that permits arbitrary code execution in the context of the user or process running the Silverlight runtime.

In practice this means the attacker crafts content that the Silverlight plugin or runtime will process; once the flawed rendering path is exercised, control flow can be diverted. No further exploit mechanics are detailed in the public summary, so defenders should treat any untrusted Silverlight content as potentially capable of achieving code execution and should not rely on incomplete public descriptions for detection signatures.

Am I affected? How to find it in your systems

Microsoft Silverlight historically appeared as a browser plug-in or runtime on Windows desktops and servers that needed to display rich internet applications. It may still be present on legacy workstations, kiosks, terminal servers, or internal web applications that were never migrated away from the technology.

Inventory steps include:

• Query installed programs and browser add-ons for any Microsoft Silverlight entries on endpoints and servers.
• Search software deployment and asset-management databases for Silverlight packages or related MSI/EXE artifacts.
• Inspect internal web applications and intranet sites for references to Silverlight (.xap files, object/embed tags that load the Silverlight runtime).
• Review group-policy or application-whitelisting configurations that may still permit the Silverlight runtime to load.

Because the product is end-of-life, any detected installation should be regarded as affected until proven otherwise; confirm version and configuration details against the vendor advisory. Telemetry signs of exploitation are not specified in the available facts, so look for unexpected process creation under browser or Silverlight-related processes, anomalous network connections originating from those processes, and any crash or fault reports tied to the Silverlight runtime. Correlate these with user reports of unexpected prompts or content from untrusted sources.

How to remediate

The primary remediation is to remove Microsoft Silverlight entirely. CISA states that the impacted product is end-of-life and should be disconnected if still in use. Uninstall the runtime from every system where it is found, and retire or rewrite any applications that depend on it.

If a vendor-supplied update was ever issued for this CVE, apply that update only as an interim step while planning full removal; always verify the exact package name and applicability in the original Microsoft advisory. After removal, validate that no residual browser plug-in registrations, file associations, or scheduled tasks remain. Harden systems by ensuring browsers no longer attempt to load Silverlight content and by enforcing application control that blocks any reintroduction of the runtime.

If you can't patch immediately

When immediate uninstall is not feasible, reduce the attack surface with the following compensating controls:

• Network segmentation: isolate hosts that still require Silverlight from general user populations and from sensitive data stores.
• Application control / allow-listing: prevent execution of the Silverlight runtime except on explicitly authorized systems.
• Disable the affected feature: remove or block Silverlight browser plug-ins via group policy or browser configuration so that crafted content cannot be rendered.
• Virtual patching / content filtering: use web proxies or secure web gateways to block download and execution of Silverlight application packages (.xap and related MIME types) from untrusted sources.
• Heightened monitoring: enable detailed process-creation and network-connection logging on remaining Silverlight hosts and alert on any unexpected child processes or outbound connections.

These measures only buy time; the durable solution remains complete disconnection of the end-of-life product.

If your data may have been exposed

Actively exploited vulnerabilities, including those known to be used by ransomware operators, frequently lead to broader compromise and data theft. If Silverlight was present on systems that handled sensitive information, assume that successful exploitation could have provided an initial foothold. Review endpoint and network logs for indicators of follow-on activity, reset credentials that may have been accessible from those hosts, and examine backup integrity. As an additional check, you can run a free exposure scan of your email addresses against known breach data sets to determine whether associated credentials or personal information have already appeared in public breach corpora.