CVE-2026-111497: What the Brotli Bug Means for .NET Developers

On October 25, 2026, Microsoft shipped an out-of-band update fixing a Critical (CVSS 8.1) out-of-bounds write in the Brotli decoder used by .NET. It may let an attacker read or corrupt process memory, leading to information disclosure, DoS, or elevation of privilege. What is Brotli? Brotli is Google’s compression algorithm, widely used on the web via Content-Encoding: br. It has two sides: the encoder (compresses) and the decoder (decompresses). The bug is in the decoder, the side that processes incoming data, which is exactly where an attacker can feed crafted input. How is .NET involved? .NET doesn’t implement Brotli itself.…








