A buffer overflow vulnerability in Google Brotli's C decoder library, tracked as CVE-2026-111497 and dubbed HTTP2Shell, has prompted emergency patches from Microsoft and other vendors after researchers determined that a remote, unauthenticated attacker can corrupt decoder memory, expose sensitive data, cause denial of service, or execute arbitrary code1,2.
Brotli versions 1.0.3 through 1.2.0 are affected. Any application that decompresses untrusted Brotli data is at risk, including NodeJS and Python applications that bundle the vulnerable decoder, as well as services that accept request bodies with the Content-Encoding: br header.
Microsoft's Azure networking security team published guidance on October 23 recommending upgrades to Brotli 1.0.10, 1.1.1, or 1.2.1. For NodeJS specifically, patched releases are 22.23.4, 24.22.1, and 26.12.1.
Organizations unable to patch immediately can use Azure Web Application Firewall on Application Gateway or Azure Front Door to mitigate the inbound attack vector, which relies on Brotli-compressed request bodies sent to an application. Microsoft cautioned that Azure WAF inspects only inbound requests and cannot protect applications that fetch and decompress Brotli-encoded responses from external servers; those applications must be patched directly.
NodeJS and Python are foundational runtimes for AI inference servers, model-serving frameworks, and agent toolchains. The vulnerability's attack surface, crafted compressed payloads delivered over HTTP, maps directly onto API endpoints that accept user-supplied content.
ANALYSIS The flaw's reach into both NodeJS and Python runtimes means AI-serving infrastructure that handles untrusted input, including LLM API gateways and agent orchestration layers, falls squarely in the blast radius.
The disclosure follows a pattern of critical vulnerabilities hitting widely deployed web runtimes. A php2shell exploit chain disclosed days earlier forced coordinated defense across an estimated 70% of the web, with exploit attempts climbing into the millions within hours of public disclosure[3].
ANALYSIS Back-to-back critical flaws in PHP and now Brotli's decoder underscore the fragility of compression and parsing layers that sit upstream of application logic.
Microsoft and BleepingComputer reporter Bill Toulas characterized the patches as emergency releases. The patched Brotli versions are available on the project's releases page.