A broad set of software stacks are affected by the Brotli flaw, including Node.js, Bun, Python Brotli and brotlicffi packages, Envoy proxies, Istio, and HTTP clients that decode Brotli data, with exposure tied to how Brotli is used in each project.

Exposure is highest for apps that fetch or decompress untrusted Brotli data, with additional risk for Bun (pre-1.4.4), Envoy, and several PyPI Python packages.

Impact varies by usage: Node.js and Bun are at risk when fetch() reads Content-Encoding: br or when request-body code decodes Brotli; Envoy/Istio are affected only if Brotli decompression is enabled; Python risk stems from installed Brotli or brotlicffi packages.

The flaw was disclosed around mid-October 2026, with fixes released by Google/Brotli maintainers and affected projects; there have been no widespread exploits demonstrated in the wild.

Proof-of-concept code surfaced, and Imperva’s research shows reliable exploitation against affected Node.js builds, emphasizing the urgency of remediation.

OpenAI identified a remote code execution vulnerability in the Brotli library, tracked as CVE-2026-111497 and nicknamed “Node2Shell,” found during internal Brotli decoder security assessments.

Severity is high across sources, with CVSS 9.2 from Google, Node.js labeling it high, Red Hat 8.1 calling it important; no confirmed widespread exploitation yet.

The core flaw is an out-of-bounds write in the unsealing step triggered by crafted compressed input, potentially allowing arbitrary code execution.

Imperva demonstrated a limited PoC on unpatched Node.js 24.22.0 for Linux ARM64; no public PoC exists across all affected platforms.

Patches began rolling out: Node.js released secure versions 22.23.4, 24.22.1, and 26.12.1 on October 21, 2026, addressing this and nine additional vulnerabilities.

The vulnerability is rated high (CVSS 9.2), unauthenticated, with potential impact on both client- and server-side applications.

The memory-corruption flaw in Google's Brotli decoder (CVE-2026-111497) can let crafted data overwrite memory, leading to crashes, memory leaks, or attacker-controlled code execution.