CriticalCVE-2013-0074

    Microsoft Silverlight Double Dereference Vulnerability (CVE-2013-0074)

    Published In CISA KEV since Sources: CVE.org

    What is affected, what to do

    Microsoft Silverlight 5, and 5 Developer Runtime, before 5.1.20125.0 does not properly validate pointers during HTML object rendering, which allows remote attackers to execute arbitrary code via a crafted Silverlight application, aka "Silverlight Double Dereference Vulnerability."

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. Update Microsoft Silverlight to version 5.1.20125.0. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Microsoft Silverlight lt 5.0..5.1.20125.0
    Fixed in
    • Microsoft Silverlight 5.1.20125.0

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    7.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    7.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: CVE.org

    78.9 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.59

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    243.35 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    7.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    78.9 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.59
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 1 July 2022

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw was exploited at scale through exploit kits in drive-by attacks: simply visiting a crafted or compromised website is enough to execute code as the logged-on user without authentication, and CISA explicitly flags known ransomware use. Despite its age it is still rated among the CVEs most likely to be exploited, because Silverlight lingers in legacy estates — particularly at critical-infrastructure operators with long application lifecycles. Where Silverlight is absent or IE11 is fully disabled, residual risk is low and verification is sufficient; any installation on an internet-capable client should be treated as a high-priority finding and removed promptly, since the component is no longer supported.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Sweep all Windows endpoints and terminal servers for Microsoft Silverlight — check registry HKLM\SOFTWARE\Microsoft\Silverlight (value Version) or query EDR/SCCM for sllauncher.exe / agcp.exe under C:\Program Files\Microsoft Silverlight\. Anything below 5.1.20125.0 is vulnerable.
      • Uninstall rather than patch: Silverlight reached end of support on 12 October 2021 and receives no further security fixes. Version 5.1.20125.0 (Security Bulletin MS13-022) fixes this specific flaw, but the component remains an attack surface. Remove it fleet-wide via MSI uninstall through software distribution or GPO.
      • Handle exceptions: Identify line-of-business apps with a hard Silverlight dependency (legacy intranet portals, control-room, video or building-management clients), escalate to the risk owner, and as a minimum bring them to 5.1.20125.0 or later until they are replaced.
      • Restrict Internet Explorer: Silverlight is realistically only reachable through IE11 or Edge IE mode. Disable IE11 via GPO and limit IE mode to an allow-list of internal sites.
      • Fix the most exposed first: Hosts that have Silverlight and unrestricted internet access (admin workstations, jump hosts, kiosks) get cleaned up first, or are cut off from direct web browsing until they are.

    2. Runbook step 2

      Mitigation layers

      • Web proxy / SWG: Block downloads with MIME type application/x-silverlight-app and .xap extensions from external sources; allow only explicitly approved internal hosts.
      • Browser hardening: Use the GPO "Add-on Management" setting to disable the Silverlight ActiveX control (CLSID {DFEAF541-F3E1-4C24-ACAC-99C30715084A}) in every zone except Local Intranet; permit Edge IE mode only through an Enterprise Site List.
      • Endpoint hardening: Use WDAC/AppLocker or EDR custom block rules to stop iexplore.exe and agcp.exe from spawning cmd.exe, powershell.exe, wscript.exe, mshta.exe or rundll32.exe.
      • Network segmentation: Move remaining Silverlight-dependent clients into a dedicated VLAN with no internet breakout, reachable only to and from the application they serve.
      • Least privilege: Run users on those clients without local admin rights to contain the impact of user-context code execution.
      • IPS signatures: Enable and set to block existing Suricata/Snort rules covering Silverlight exploit-kit traffic (ET "EXPLOIT_KIT" / "CURRENT_EVENTS" categories referencing Silverlight).

    3. Runbook step 3

      Detection rules

      • EDR / Sysmon EID 1 — process ancestry: Script interpreters or LOLBins spawned by iexplore.exe or agcp.exe. KQL: DeviceProcessEvents | where InitiatingProcessFileName in~ ("iexplore.exe","agcp.exe") | where FileName in~ ("cmd.exe","powershell.exe","wscript.exe","cscript.exe","mshta.exe","rundll32.exe","regsvr32.exe")
      • Sysmon EID 11 — file creation: Executables (.exe, .dll, .scr) dropped into %TEMP% or %APPDATA% by iexplore.exe/agcp.exe shortly after a .xap fetch.
      • Proxy / Zeek http.log: Requests with mime_type == "application/x-silverlight-app" or URIs ending in .xap from unapproved, newly registered or uncategorised domains; correlate with preceding redirect chains (malvertising, compromised sites).
      • Windows Event ID 1000 (Application Error): Crashes of agcp.exe or iexplore.exe with faulting module npctrl.dll or coreclr.dll — a sign of failed exploitation attempts.
      • Ransomware follow-on: After any hit above, hunt the same host for vssadmin delete shadows, wbadmin delete catalog or bulk file renames (Sysmon EID 11/EID 23).

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Microsoft Silverlight 5, and 5 Developer Runtime, before 5.1.20125.0 does not properly validate pointers during HTML object rendering, which allows remote attackers to execute arbitrary code via a crafted Silverlight application, aka "Silverlight Double Dereference Vulnerability."

    Source: CISA KEV Catalog, cvelistv5, NVD (NIST), CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    microsoftsilverlight
    • 5.0 – < 5.1.20125.0
    • 5.1.20125.0

    Vendors and products

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited

    References & sources

    • oval.cisecurity.orgoval:org.mitre.oval:def:16565Vulnerability database, signature, x_refsource_OVAL
    • oval.cisecurity.orgoval:org.mitre.oval:def:16516Vulnerability database, signature, x_refsource_OVAL
    • us-cert.govTA13-071AThird-party advisory, x_refsource_CERT
    • docs.microsoft.comMS13-022Vendor advisory, x_refsource_MS
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2013-0074government-resource
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