PYSEC-2026-4323

Vulnerability from pysec - Published: 2026-10-23 00:00 - Updated: 2026-10-23 00:00
VLAI
Details

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 original 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 brotlicffi 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.

Severity
9.2 (Critical)
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
Impacted products
Name purl
brotlicffi pkg:pypi/brotlicffi
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "brotlicffi",
        "purl": "pkg:pypi/brotlicffi"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.2.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.8.0",
        "1.0.9.0",
        "1.0.9.1",
        "1.0.9.2",
        "1.1.0.0",
        "1.2.0.0",
        "1.2.0.1",
        "1.2.0.2"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-111497"
  ],
  "details": "CVE-2026-111497 (\"Node2Shell\") is an out-of-bounds write (CWE-787) in Google\u0027s\nBrotli decoder (c/dec/decode.c). DecodeBlockTypeAndLength() returns an ambiguous\nvalue for an invalid block switch, and the fast decode path discards it\n(CWE-252, unchecked return value), so a crafted Brotli stream makes the decoder\ncontinue on corrupted state and write past the ring buffer. Upstream rates it\nCVSS 4.0 9.2 and classifies the impact as potential remote code execution.\n\nThe vulnerability is in Google\u0027s C library, not in Node.js specifically. The\nPyPI `Brotli` package is Google\u0027s CPython binding and compiles the same\nc/dec/decode.c that has the original vulnerability. All `Brotli` releases up to\nand including 1.2.0 ship the vulnerable decoder; 1.2.1 contains the upstream\nfix (commit 0ed4268a) and differs from 1.2.0 only in that fix plus a version\nbump.\n\nThe decoder is reached whenever untrusted Brotli data is decompressed. With\n`brotlicffi` installed, common HTTP clients decode Brotli responses automatically\n(urllib3/requests, httpx with the brotli extra, aiohttp) and services that\naccept `Content-Encoding: br` request bodies decode inbound data, so the flaw\nis reachable from attacker-controlled input.\n",
  "id": "PYSEC-2026-4323",
  "modified": "2026-10-23T00:00:00Z",
  "published": "2026-10-23T00:00:00Z",
  "references": [
    {
      "type": "FIX",
      "url": "https://github.com/google/brotli/commit/0ed4268a4401abcb4472096340477cf4af7d1a2b"
    },
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-111497"
    },
    {
      "type": "WEB",
      "url": "https://opensourcemalware.com/blog/node2shell-affects-python"
    },
    {
      "type": "WEB",
      "url": "https://nodejs.org/en/blog/vulnerability/october-2026-security-releases"
    },
    {
      "type": "WEB",
      "url": "https://github.com/google/brotli/releases/tag/v1.2.1"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/brotlicffi/"
    }
  ],
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Out-of-bounds write in the brotlicffi decoder (\"Node2Shell\") also affects the PyPI Brotli package"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.