Google: CVE-2026-111497 Buffer overflow vulnerability in the Brotli decoder
Google: CVE-2026-111497 Buffer overflow vulnerability in the Brotli decoder. Microsoft rates it Critical; not reported as exploited; publicly disclosed; exploitability assessment: Exploitation More Likely. Microsoft publishes a customer-installable fix (KB5133964, KB5133965, KB5133966 and others listed in the advisory and release notes). Microsoft documents a mitigation or workaround.
What you should do
If you run the affected products, install Microsoft's update (KB5133964, KB5133965, KB5133966 and others listed in the advisory and release notes); the advisory lists the exact build per product. If you run the affected products, review Microsoft's documented mitigation: Brotli decompression is not enabled by default in an out-of-the-box .NET or ASP.NET Core install. Applications must manually opt in to ASP.NET Core request decompression or HttpClient response… from Microsoft's advisory data
Why: Microsoft lists a customer-installable fix and reports it as publicly disclosed, so it matters if you run the affected products.
Details
Original Microsoft text
Out-of-bounds write in .NET allows an unauthorized attacker to elevate privileges over a network.
- Severity
- Critical · CVSS 8.1
- Type
- Security updates
- Tags
- .NET, Elevation of Privilege, 2026-Oct
- Microsoft advisory data
- Customer action required: Yes · Exploited: No · Publicly disclosed: Yes · Exploitation More Likely · Remediation: update and mitigation
- Classification
- Derived from Microsoft's structured advisory fields, not by AI. Severity (Critical) is Microsoft's rating and is not treated as proof that action is needed.