.NET: Brotli compression flaw

.NET

Microsoft releases emergency .NET security fixes for Google Brotli bug

Do this now

Install the Microsoft .NET security fixes for the Brotli bug on all affected .NET hosts.

First seen: 26 Oct 2026
Last update: 26 Oct 2026, 19:18 UTC
Source: news
On the menu as: .NET

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## .NET: Brotli compression flaw
Severity: unknown. Patch status: patched.
Affected: .NET

Microsoft releases emergency .NET security fixes for Google Brotli bug

## Steps
1. Search the repo, its CI and infra config for .NET. If present, report the version in use and whether it's affected.

## Report
A table: file, product or package, version in use, affected yes/no, exact fix. Then anything a human has to check outside the repo.

If you have the pwned.coffee MCP server (https://pwned.coffee/mcp), call lookup_cve for the latest, and check_repo with this repo's lockfiles, Dockerfiles and workflows for a full receipt.
Sources: https://www.theregister.com/security/2026/10/26/microsoft-releases-emergency-net-security-fixes-for-google-brotli-bug/5305515
https://pwned.coffee/i/net-brotli-compression-flaw

Timeline

26 Oct 2026, 19:18 UTC
Fix status: unknown → patched.
26 Oct 2026, 18:17 UTC
Fix status: patched → unknown.
26 Oct 2026
First reported.

Receipt

Exploitation: No known exploitation
Fix: In addition to .NET, Node.js, and Python, Bun , Envoy , and Istio have all released patches, and JFrog has worked up an exploit affecting FFmpeg using a specially crafted JPEG XL image, extending the exploit path beyond HTTP.
Score: No CVSS published yet: severity unknown.
Last checked: 26 Oct 2026, 19:18 UTC

Sources: KEV – CVE record – Vendor –

Sources

api.theregister.com: Microsoft releases emergency .NET security fixes for Google Brotli bug

Wrong fix version, or a source we missed? Send it back to chef@pwned.coffee with the source, and we'll correct it here.

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