---
id: "CVE-2016-0034"
kind: "vulnerability"
aliases: ["CVE-2016-0034"]
title: "Microsoft Silverlight 5 before 5.1.41212.0 mishandles negative offsets during decoding, which allows remote\u2026"
severity: "critical"
cvss: 9.3
epss: 0.69397
exploited: true
status: "open"
category: "runtime"
products: [{"name": "microsoft silverlight", "fixed": ["5.1.41212.0"], "affected": ">= 5.0, < 5.1.41212.0", "ecosystem": "vendor"}, {"name": "Microsoft Silverlight", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["browsers", "exploited", "ransomware", "runtime", "silverlight", "windows"]
not_affected_if: ["no-silverlight-installed"]
published_at: "2016-01-13T05:59:22+00:00"
first_seen_at: "2026-10-23T19:11:52+00:00"
updated_at: "2026-10-24T00:09:51+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2016-0034", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2016-0034", "first_seen_at": "2026-10-23T19:13:45+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2016-0034", "first_seen_at": "2026-10-23T22:29:04+00:00"}]
---

# Microsoft Silverlight 5 before 5.1.41212.0 mishandles negative offsets during decoding, which allows remote…

Microsoft Silverlight's runtime mishandles negative offsets during decoding, letting a crafted input cause remote code execution or a denial of service. CISA lists it as actively exploited, and the sources note ransomware use.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:microsoft silverlight affected >= 5.0, < 5.1.41212.0 fixed 5.1.41212.0
- vendor:Microsoft Silverlight affected ? fixed ?

## How to check

Check whether Silverlight is installed on Windows machines (Add or remove programs, or the Silverlight Configuration app); unknown for a specific command.

## Fix

Remove Silverlight, since the product is end-of-life and no longer receives fixes (per CISA: disconnect if still in use).

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2016-0034
- 2026-10-23T19:13:45+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2016-0034
- 2026-10-23T22:29:04+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2016-0034

## From the sources

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."

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_