CVE-2016-0034 Microsoft Silverlight Runtime Remote Code Execution Vulnerability
Microsoft Silverlight mishandles negative offsets during decoding, which allows attackers to execute remote code or cause a denial-of-service (DoS).
From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.
Should You Worry?
- CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 25 May 2022.
- CISA lists it as known to be used in ransomware campaigns.
- Rated High severity (CVSS 8.8, scored by CISA).
- It has been in the catalogue for 1,626 days. Systems still unpatched now have almost certainly been scanned for it.
What It Is
Microsoft Silverlight 5 before 5.1.41212.0 mishandles negative offsets during decoding, which allows remote attackers to execute arbitrary code or cause a denial of service (object-header corruption) via a crafted web site, aka "Silverlight Runtime Remote Code Execution Vulnerability."
What To Do Now
- 1
Find it
Search your asset inventory and external attack surface for Microsoft Silverlight. Include cloud images, appliances and anything a supplier runs for you.
Attack Surface Management - 2
Fix it
The impacted products are end-of-life and should be disconnected if still in use.
Vulnerability Management - 3
Hunt for compromise
If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.
Incident Response - 4
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing
Vendor Advisories
The Compliance Clock
General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.
Not Sure If You Are Exposed?
Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2016-0034 and every other exploited flaw on the list.