PYSEC-2026-3472

Vulnerability from pysec - Published: 2026-07-23 11:41 - Updated: 2026-07-23 14:31
VLAI
Details

A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the allow_origin_pat configuration is used. The issue arises from the use of re.match() for validating the Origin header, which only anchors at the start of the string. This allows attacker-controlled domains such as trusted.example.com.evil.com to pass validation against patterns intended to match trusted.example.com. The vulnerability affects multiple locations in the codebase, including CORS headers, WebSocket connections, referer validation, and login redirects, potentially enabling phishing attacks, arbitrary code execution, and unauthorized access to sensitive API responses.

Severity
6.1 (Medium)
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Impacted products
Name purl
jupyter-server pkg:pypi/jupyter-server
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "jupyter-server",
        "purl": "pkg:pypi/jupyter-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.12.0"
            },
            {
              "last_affected": "2.17.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.12.0",
        "1.12.1",
        "1.13.0",
        "1.13.1",
        "1.13.2",
        "1.13.3",
        "1.13.4",
        "1.13.5",
        "1.15.0",
        "1.15.1",
        "1.15.2",
        "1.15.3",
        "1.15.4",
        "1.15.5",
        "1.15.6",
        "1.16.0",
        "1.17.0",
        "1.17.1",
        "1.18.0",
        "1.18.1",
        "1.19.0",
        "1.19.1",
        "1.21.0",
        "1.23.0",
        "1.23.1",
        "1.23.2",
        "1.23.3",
        "1.23.4",
        "1.23.5",
        "1.23.6",
        "1.24.0",
        "2.0.0",
        "2.0.0a0",
        "2.0.0a1",
        "2.0.0a2",
        "2.0.0b0",
        "2.0.0b1",
        "2.0.0rc0",
        "2.0.0rc1",
        "2.0.0rc2",
        "2.0.0rc3",
        "2.0.0rc4",
        "2.0.0rc5",
        "2.0.0rc6",
        "2.0.0rc7",
        "2.0.0rc8",
        "2.0.1",
        "2.0.2",
        "2.0.3",
        "2.0.4",
        "2.0.5",
        "2.0.6",
        "2.0.7",
        "2.1.0",
        "2.10.0",
        "2.10.1",
        "2.11.0",
        "2.11.1",
        "2.11.2",
        "2.12.0",
        "2.12.1",
        "2.12.2",
        "2.12.3",
        "2.12.4",
        "2.12.5",
        "2.13.0",
        "2.14.0",
        "2.14.1",
        "2.14.2",
        "2.15.0",
        "2.16.0",
        "2.17.0",
        "2.2.0",
        "2.2.1",
        "2.3.0",
        "2.4.0",
        "2.5.0",
        "2.6.0",
        "2.7.0",
        "2.7.1",
        "2.7.2",
        "2.7.3",
        "2.8.0",
        "2.9.0",
        "2.9.1"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-6657",
    "GHSA-v42x-x7jp-845h"
  ],
  "details": "A vulnerability in jupyter-server versions 1.12.0 through 2.17.0 allows an attacker to bypass CORS origin validation when the `allow_origin_pat` configuration is used. The issue arises from the use of `re.match()` for validating the `Origin` header, which only anchors at the start of the string. This allows attacker-controlled domains such as `trusted.example.com.evil.com` to pass validation against patterns intended to match `trusted.example.com`. The vulnerability affects multiple locations in the codebase, including CORS headers, WebSocket connections, referer validation, and login redirects, potentially enabling phishing attacks, arbitrary code execution, and unauthorized access to sensitive API responses.",
  "id": "PYSEC-2026-3472",
  "modified": "2026-07-23T14:31:21.011689Z",
  "published": "2026-07-23T11:41:37.761563Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-6657"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jupyter-server/jupyter_server"
    },
    {
      "type": "WEB",
      "url": "https://huntr.com/bounties/18f642db-3569-43b3-b58d-ff97be4b09d7"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/jupyter-server"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-v42x-x7jp-845h"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "jupyter-server is vulnerable to CORS origin validation bypass when the `allow_origin_pat` configuration is used"
}



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