ubuntu-cve-2020-26891
Vulnerability from osv_ubuntu
Published
2020-10-19 17:15
Modified
2025-10-24 04:48
Summary
Details

AuthRestServlet in Matrix Synapse before 1.21.0 is vulnerable to XSS due to unsafe interpolation of the session GET parameter. This allows a remote attacker to execute an XSS attack on the domain Synapse is hosted on, by supplying the victim user with a malicious URL to the /_matrix/client/r0/auth//fallback/web or /_matrix/client/unstable/auth//fallback/web Synapse endpoints.

Severity
6.1 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "matrix-synapse",
            "binary_version": "0.24.0+dfsg-1ubuntu0.1~esm4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "matrix-synapse",
        "purl": "pkg:deb/ubuntu/matrix-synapse@0.24.0+dfsg-1ubuntu0.1~esm4?arch=source\u0026distro=esm-apps/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.19.2+dfsg-6",
        "0.24.0+dfsg-1",
        "0.24.0+dfsg-1ubuntu0.1~esm1",
        "0.24.0+dfsg-1ubuntu0.1~esm4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "matrix-synapse",
            "binary_version": "1.11.0-1ubuntu0.1~esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "matrix-synapse",
        "purl": "pkg:deb/ubuntu/matrix-synapse@1.11.0-1ubuntu0.1~esm2?arch=source\u0026distro=esm-apps/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.3.0-1",
        "1.4.0-1",
        "1.5.0-1",
        "1.5.1-1",
        "1.6.0-1",
        "1.6.1-1",
        "1.7.0-2",
        "1.7.1-1",
        "1.7.2-1",
        "1.7.3-1",
        "1.8.0-1",
        "1.9.0-1",
        "1.9.1-1",
        "1.10.0-1",
        "1.10.0-2",
        "1.11.0-1",
        "1.11.0-1ubuntu0.1~esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "matrix-synapse",
            "binary_version": "1.53.0-1ubuntu0.1~esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:22.04:LTS",
        "name": "matrix-synapse",
        "purl": "pkg:deb/ubuntu/matrix-synapse@1.53.0-1ubuntu0.1~esm2?arch=source\u0026distro=esm-apps/jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.39.0-1",
        "1.47.0-2",
        "1.47.1-1",
        "1.48.0-1",
        "1.49.0-1",
        "1.49.2-1",
        "1.50.1-1",
        "1.50.2-1",
        "1.51.0-1",
        "1.52.0-1",
        "1.53.0-1",
        "1.53.0-1ubuntu0.1~esm2"
      ]
    }
  ],
  "aliases": [],
  "details": "AuthRestServlet in Matrix Synapse before 1.21.0 is vulnerable to XSS due to unsafe interpolation of the session GET parameter. This allows a remote attacker to execute an XSS attack on the domain Synapse is hosted on, by supplying the victim user with a malicious URL to the /_matrix/client/r0/auth/*/fallback/web or /_matrix/client/unstable/auth/*/fallback/web Synapse endpoints.",
  "id": "UBUNTU-CVE-2020-26891",
  "modified": "2025-10-24T04:48:49Z",
  "published": "2020-10-19T17:15:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2020-26891"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/matrix-org/synapse/pull/8444"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/matrix-org/synapse/releases"
    },
    {
      "type": "REPORT",
      "url": "https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisory"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2020-26891"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2020-26891"
  ]
}



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