Brotli flaw exposes Python packages to remote code execution

CVE-2026-111497, known as Node2Shell, is a memory-safety flaw in Google’s Brotli decoder that can cause an out-of-bounds write. The vulnerability affects Brotli upstream versions 1.0.3 through 1.2.0, with a CVSS v4.0 score of 9.2. Google published the record on 22 October 2026, and the fix landed in Brotli 1.0.10, 1.1.1 and 1.2.1 on 21 October 2026.

Public demonstrations showed potential remote code execution against Node.js through the same decoder code, which underlines the risk of the bug when untrusted Brotli data is processed.

Python exposure comes via two PyPI native extensions that bundle Google’s decoder: Brotli 1.2.0 and earlier, and brotlicffi 1.2.0.x and earlier. The fixed versions are Brotli 1.2.1 and brotlicffi 1.2.1.0. Because urllib3, requests, httpx and aiohttp can decode Brotli automatically when a backend is installed, Python applications can be exposed without any Brotli import in their own code.

As of 26 October 2026, no in-the-wild exploitation had been reported for Python, though Node.js-related RCE research confirms the underlying decoder vulnerability. Authors caution that dependency scans may miss the PyPI packages, since they can be transitive or bundled in other projects.

To mitigate, upgrade to the fixed Python packages, rebuild images and restart long-running workers so the patched decoder loads. If patching is not immediately possible, remove Brotli usage or block br-encoded content at proxies and decoders, then verify that the loaded extension is the updated one. The disclosure notes no public PoC for Python memory corruption or execution, but cautions that the shared decoder flaw remains a broader risk across runtimes.