CVE-2016-0034
CVE-2016-0034 is a security flaw in Microsoft Silverlight, Microsoft’s discontinued browser plug-in. Attackers can run their own code on Microsoft Silverlight. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 25 May 2022, and says ransomware gangs have used it.[1]
Microsoft Silverlight is in things households have, such as phones, computers, browsers and everyday apps, so the fix matters at home as much as at work. Microsoft has published a fix or advice.
Description
CISA calls it a runtime remote code execution in Microsoft Silverlight. In its words: “Microsoft Silverlight mishandles negative offsets during decoding, which allows attackers to execute remote code or cause a denial-of-service (DoS).”[1]
The CVE record adds: “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."”[2]
The underlying weakness is improper input validation (CWE-20), in MITRE’s list of common software weaknesses.
It scores 8.8 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Microsoft’s advisory has them[3]. CISA names the product as Microsoft Silverlight.
Every device with Microsoft Silverlight needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 25 May 2022, 2,324 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 15 Jun 2022 to fix it.[1] CISA says ransomware gangs have used it.
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 69%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Microsoft has published a fix or advice.[3] CISA’s required action: “The impacted products are end-of-life and should be disconnected if still in use.”[1]
- Update Microsoft Silverlight now.Install the latest update from Microsoft on every device that has it, and restart when asked. Then turn on automatic updates, so the next fix arrives on its own.
- If there’s no update, stop using it.CISA’s advice when a flaw being used in attacks has no fix is to stop using the product until it does.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 69%.[4] |
See also
Other Microsoft Silverlight flaws
- CVE-2013-3896: information disclosure ·
- CVE-2013-0074: double dereference ·
Other Microsoft flaws
- CVE-2026-96951, Microsoft Windows: command injection ·
- CVE-2026-65660, Microsoft SharePoint: code injection ·
- CVE-2026-85880, Microsoft Windows: heap-based buffer overflow ·
- CVE-2026-81963, Microsoft Windows: link following ·
- CVE-2019-1068, Microsoft SQL Server: remote code execution ·
Other improper input validation flaws
- CVE-2026-93952, Arista VeloCloud Orchestrator: improper input validation ·
- CVE-2026-12569, PTC Windchill and FlexPLM: improper input validation ·
- CVE-2026-34910, Ubiquiti UniFi OS: improper input validation ·
- CVE-2026-6973, Ivanti Endpoint Manager Mobile (EPMM): improper input validation ·
- CVE-2026-34197, Apache ActiveMQ: improper input validation ·
Added the same day
- CVE-2019-3010, Oracle Solaris: privilege escalation ·
- CVE-2016-7256, Microsoft Windows: open type font remote code execution ·
- CVE-2016-3393, Microsoft Windows: graphics device interface (GDI) remote code execution ·
- CVE-2016-1010, Adobe Flash Player and AIR: integer overflow ·
- CVE-2016-0984, Adobe Flash Player and AIR: use-after-free ·
Every Microsoft flaw on CISA’s list · Everything added in May 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “Microsoft Silverlight Runtime Remote Code Execution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 25 May 2022.
- ^ National Institute of Standards and Technology. “CVE-2016-0034 Detail”. National Vulnerability Database, published 13 Jan 2016.
- ^ Microsoft. Advisories and fixes: docs.microsoft.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.694, percentile 99.4, 31 Oct 2026.
- CVE Program. “CVE-2016-0034”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.