Out-of-bounds write in the Brotli decoder ("Node2Shell") also affects the PyPI Brotli package
CVE-2026-111497 ("Node2Shell") is an out-of-bounds write (CWE-787) in Google's Brotli decoder (c/dec/decode.c). DecodeBlockTypeAndLength() returns an ambiguous value for an invalid block switch, and the fast decode path discards it (CWE-252, unchecked return value), so a crafted Brotli stream makes the decoder continue on corrupted state and write past the ring buffer. Upstream rates it CVSS 4.0 9.2 and classifies the impact as potential remote code execution.
The vulnerability is in Google's C library, not in Node.js specifically. The
PyPI Brotli package is Google's CPython binding and compiles the same
c/dec/decode.c that has the actual vulnerability. All Brotli releases up to
and including 1.2.0 ship the vulnerable decoder; 1.2.1 contains the upstream
fix (commit 0ed4268a) and differs from 1.2.0 only in that fix plus a version
bump.
The decoder is reached whenever untrusted Brotli data is decompressed. With
Brotli installed, common HTTP clients decode Brotli responses automatically
(urllib3/requests, httpx with the brotli extra, aiohttp) and services that
accept Content-Encoding: br request bodies decode inbound data, so the flaw
is reachable from attacker-controlled input.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | brotli | < 1.2.1 | 1.2.1 |
| Python (PyPI) | brotlicffi | < 1.2.1.0 | 1.2.1.0 |
References
- https://github.com/google/brotli/commit/0ed4268a4401abcb4472096340477cf4af7d1a2b
- https://www.cve.org/CVERecord?id=CVE-2026-111497
- https://opensourcemalware.com/blog/node2shell-affects-python
- https://nodejs.org/en/blog/vulnerability/october-2026-security-releases
- https://github.com/google/brotli/releases/tag/v1.2.1
- https://pypi.org/project/brotlicffi/
- https://pypi.org/project/Brotli/
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N- Weakness (CWE)
-- Platform
- Python (PyPI)
- Package
brotli, brotlicffi- Disclosed
- 23.10.2026
- Updated
- 23.10.2026 16:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-4323 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - PYSEC-2026-4322 - PyPA Advisory Database; CC BY 4.0
Vulnerability history: brotlicffi
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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