Critical Advisory: Resolving CVE-2013-0074 and the Risks of Legacy Microsoft Silverlight Deployments
Microsoft Silverlight does not properly validate pointers during HTML object rendering, which allows remote attackers to execute code via a crafted Silverlight application.
FREQUENTLY ASKED
What is CVE-2013-0074 and why does it matter?
CVE-2013-0074 is a critical vulnerability in Microsoft Silverlight known as a Double Dereference Vulnerability. It allows remote attackers to execute arbitrary code on a target system by tricking a user into visiting a page with a crafted Silverlight application. With a CVSS score of 7.8 and active exploitation history, it represents a significant risk to systems still running legacy browser plugins.
Which versions of Microsoft Silverlight are affected?
The vulnerability affects Microsoft Silverlight 5 and the Silverlight 5 Developer Runtime for versions prior to 5.1.20125.0. Because the product reached its end-of-life (EOL) status, all installations remaining in production environments should be considered potentially vulnerable and subject to immediate decommissioning.
Has a patch been released for CVE-2013-0074?
Yes, Microsoft originally addressed this issue in security bulletin MS13-022. However, because Silverlight is now an end-of-life product, the primary security recommendation is no longer just patching, but the complete removal of the software. If legacy systems still require the plugin, they must be isolated from the internet to prevent exploitation.
What is the remediation deadline and what does it mean for compliance?
The remediation deadline for CVE-2013-0074 was 2022-06-15, following its addition to the CISA Known Exploited Vulnerabilities (KEV) catalog. For federal agencies and organizations following CISA BOD 22-01, failure to decommission or secure the affected product by this date results in non-compliance with mandatory cybersecurity directives.
How can I check if an instance or deployment is affected?
Administrators should audit their environments for the presence of the Silverlight.exe or related browser extensions. Specifically, check the version of the Silverlight runtime; if it is lower than 5.1.20125.0, it is vulnerable. Given its EOL status, the presence of any Silverlight version should be flagged as a security risk during vulnerability scans.
CVE-2013-0074 represents a high-severity remote code execution (RCE) vulnerability within Microsoft Silverlight, carrying a CVSS score of 7.8. This specific flaw, categorized as a "Double Dereference Vulnerability," stems from the application's failure to properly validate pointers during the rendering of HTML objects. Given its inclusion in the CISA Known Exploited Vulnerabilities (KEV) catalog and its confirmed use in ransomware campaigns, the remediation deadline of 2022-06-15 underscores an urgent need for organizations to decommission this end-of-life (EOL) product immediately.
Vulnerability Profile Table
Field
Value
CVE ID
CVE-2013-0074
Affected Product & Versions
Microsoft Silverlight 5, 5 Developer Runtime < 5.1.20125.0
CVSS Score & Severity
7.8 (HIGH)
CVSS Version
3.1
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack Vector
LOCAL (via Remote Application)
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
CWE IDs
CWE-noinfo
Date Disclosed
2022-05-25
Remediation Deadline
2022-06-15
SSVC Exploitation Status
Active
Known Ransomware Use
Yes
EPSS Score & Percentile
0.93187 (99.8%)
Patch Available
Yes (MS13-022)
Technical Deep Dive: The Mechanics of Double Dereferencing
Understanding Pointer Validation Failures
While the source data classifies the specific CWE as "noinfo," the vulnerability name—the Silverlight Double Dereference Vulnerability—provides significant insight into the underlying flaw. In systems programming, a pointer is a variable that holds the memory address of another value. "Dereferencing" is the act of accessing the data stored at that address.
A double dereference occurs when a pointer points to a second pointer, which in turn points to the actual data. Vulnerabilities arise when the software fails to validate the integrity of the first pointer before following the link to the second. In the context of CVE-2013-0074, Microsoft Silverlight's HTML object rendering engine fails to verify these pointer chains. If a threat actor can control the memory location where the first pointer resides, they can redirect the second dereference to a memory address of their choosing. This often leads to an "arbitrary write" or "arbitrary read" scenario, providing the foundation for full system compromise.
The Attack Chain and Blast Radius
To exploit this flaw, an attacker typically hosts a specially crafted Silverlight application on a malicious website or embeds it within a compromised legitimate site. The attack chain proceeds as follows:
Luring the Target: The user is directed to a URL containing the malicious Silverlight content. Because the Attack Vector is classified as Local but triggered via a remote application, the exploit relies on the browser's plugin execution environment.
Memory Manipulation: The malicious Silverlight application triggers the HTML rendering process. Due to the lack of pointer validation, the application forces the Silverlight runtime to follow a corrupted pointer.
Code Execution: By carefully timing the memory manipulation, the attacker redirects the execution flow to their shellcode. Because Silverlight often runs with the privileges of the logged-in user, the attacker gains the ability to execute commands, install software, or exfiltrate data.
The blast radius for CVE-2013-0074 is substantial. Since Silverlight was a cross-browser plugin, it affected users across various web environments. Furthermore, its inclusion in ransomware kits indicates that this vulnerability served as an initial entry point for large-scale encryption attacks, leveraging the high EPSS score of 0.93187 to identify target-rich environments with unpatched legacy software.
Who Is Affected: Identifying At-Risk Infrastructure
Organizations most at risk are those maintaining legacy web applications that rely on Microsoft Silverlight for rich media or interactive content. This frequently includes internal enterprise portals, legacy financial dashboards, and industrial control system (ICS) web interfaces designed in the early 2010s.
In accordance with CISA Binding Operational Directive (BOD) 22-01, all federal civilian executive branch agencies were required to remediate this vulnerability by June 15, 2022. For the private sector, this deadline serves as a critical benchmark. If your organization still maintains Silverlight 5 or the Developer Runtime versions prior to 5.1.20125.0, you are operating outside of established security baselines and are actively targeted by threat actors who specialize in exploiting "long-tail" legacy vulnerabilities.
Official Remediation Steps and EOL Guidance
As Microsoft Silverlight reached its end of support on October 12, 2021, the remediation strategy has shifted from routine patching to total decommissioning. Follow these steps to secure your environment:
Immediate Decommissioning: The primary recommendation is to uninstall Microsoft Silverlight from all workstations and servers. Use centralized management tools (such as Microsoft Endpoint Configuration Manager or Group Policy) to identify and remove the software.
Patching Legacy Instances: If a mission-critical system cannot be immediately updated and requires Silverlight, ensure it is running at least version 5.1.20125.0. Refer to Microsoft Security Bulletin MS13-022 for historical patch data, though note that this does not protect against vulnerabilities discovered after 2021.
Browser Hardening: Disable the Silverlight plugin within web browsers (Internet Explorer, legacy Edge, or Firefox) via Administrative Templates. Modern browsers no longer support NPAPI/ActiveX plugins, which inherently mitigates the attack surface.
Network Segmentation: For systems that absolutely require Silverlight for legacy operations, isolate these machines from the internet. Use a jump box or a restricted VLAN to ensure the Silverlight-enabled browser cannot navigate to external, attacker-controlled websites.
Security Best Practices for Legacy Mitigation
To prevent similar risks associated with memory corruption and legacy software, organizations should adopt the following defensive posture:
Software Inventory Management: Maintain a dynamic Asset Inventory that flags any software approaching its End-of-Life date at least 18 months in advance.
Implement Attack Surface Reduction (ASR): Use ASR rules to block the execution of unsigned or low-reputation plugins within the browser environment.
Memory Protection Mechanisms: Ensure that Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) are enforced globally. While CVE-2013-0074 targets pointer validation, these OS-level protections make exploitation significantly more difficult.
Zero Trust Browser Isolation: For users who must access potentially high-risk legacy content, utilize Remote Browser Isolation (RBI) technology. This executes the web content in a disposable container, preventing RCE vulnerabilities like CVE-2013-0074 from reaching the local endpoint.
Vulnerability Prioritization: Utilize EPSS (Exploit Prediction Scoring System) data to prioritize the removal of software with high exploitation probability (like Silverlight's 99.8th percentile) over theoretical risks.
Phasing Out ActiveX/NPAPI: Transition all internal applications to modern HTML5/WebAssembly standards, which provide superior performance and built-in security sandboxing compared to legacy plugin architectures.