PYSEC-2026-843

Vulnerability from pysec - Published: 2026-07-06 08:03 - Updated: 2026-07-06 08:03
VLAI
Details

util/emailutils.py in Matrix Sydent before 1.0.2 mishandles registration restrictions that are based on e-mail domain, if the allowed_local_3pids option is enabled. This occurs because of potentially unwanted behavior in Python, in which an email.utils.parseaddr call on user@bad.example.net@good.example.com returns the user@bad.example.net substring.

Severity
5.9 (Medium)
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Impacted products
Name purl
matrix-sydent pkg:pypi/matrix-sydent
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "matrix-sydent",
        "purl": "pkg:pypi/matrix-sydent"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2019-11340",
    "GHSA-q9h8-gpw5-c95c"
  ],
  "details": "util/emailutils.py in Matrix Sydent before 1.0.2 mishandles registration restrictions that are based on e-mail domain, if the allowed_local_3pids option is enabled. This occurs because of potentially unwanted behavior in Python, in which an email.utils.parseaddr call on user@bad.example.net@good.example.com returns the user@bad.example.net substring.",
  "id": "PYSEC-2026-843",
  "modified": "2026-07-06T08:03:28.015702Z",
  "published": "2026-07-06T08:03:28.015702Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-11340"
    },
    {
      "type": "WEB",
      "url": "https://github.com/matrix-org/sydent/commit/4e1cfff53429c49c87d5c457a18ed435520044fc"
    },
    {
      "type": "WEB",
      "url": "https://github.com/matrix-org/sydent/compare/7c002cd...09278fb"
    },
    {
      "type": "WEB",
      "url": "https://matrix.org/blog/2019/04/18/security-update-sydent-1-0-2"
    },
    {
      "type": "WEB",
      "url": "https://twitter.com/matrixdotorg/status/1118934335963500545"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/matrix-sydent"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-q9h8-gpw5-c95c"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Matrix Sydent mishandles emails"
}



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