This week's "node2shell" Brotli vulnerability (CVE-2026-111497) is exploitable in Python, other consumers of Brotli

TL;DR⚠️ Brotli is a widely used compression library from Google. On Wednesday, October 21st NodeJS disclosed CVE-2026-111497, dubbed “node2shell,” wherein a Node.js process that decompresses attacker-controlled Brotli data can be made to leak memory or run arbitrary code. On Thursday, Python disclosed that Python packages were vulnerable to CVE-2026-111497 as well.On Friday, October 23rd, it has become known that this CVE affects other major languages and service applications using HTTP, where patches are not yet fully available.Check if you are decoding Brotli as a dependency within your libraries. Stay on guard for wider announcements and be ready to upgrade as soon as possible. If there is no patch available for a library or application that may be affected, we recommend disabling Brotli decoding until patches become available.Update 4:12PM PT: Patches are available for libbrotli, Python, C++, NodeJS, bun, Envoy and more coming. Apache and Nginx do not decode brotli by default.Update 4:15 PM PT: OpenAI shares that they discovered this vulnerability in February. While the root cause issue was fixed in the Brotli source code at the time, it wasn’t known that it gave rise to a security vulnerability. OpenAI's advisories here. ‍What is Brotli?Brotli is a lossless compression algorithm and data format developed by Google. It’s a way to make data smaller for storage or sending over the internet. Software then unpacks it to recover the original data. It’s widely used for HTTP compression to compress web content such as HTML, CSS, and JavaScript.What is CVE-2026-111497?CVE-2026-111497 is an out-of-bounds write in the Google Brotli decoder affecting versions 1.0.3 through 1.2.0 on all platforms. This is the same Brotli decoder flaw behind Node2Shell announced a couple days ago. A remote, unauthenticated attacker can send a crafted Brotli-compressed stream to corrupt memory, leak sensitive data, crash the process, or potentially execute arbitrary code. It carries a CVSS v4.0 score of 9.2 (Critical), and Node.js is affected through its bundled Brotli library.A bug makes the Brotli decoder keep accepting more bytes when it should reject the data. Those bytes can overflow a small working buffer and damage the program’s memory. An attacker can use that damage to control what runs, such as their own code.OpenAI found this in February reported it as unauthenticated remote code execution that works in both directions, so a malicious client can take over an unpatched …