{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "4.5.0"
              },
              {
                "fixed": "4.5.8"
              }
            ]
          },
          "events": [
            {
              "introduced": "26c78392f88afccebb8a88b68bc9994a9ce12648"
            },
            {
              "fixed": "38e7bb9b866b5d207a511de093de25536f13e9c4"
            }
          ],
          "repo": "https://github.com/mastodon/mastodon",
          "type": "GIT"
        },
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "4.4.0"
              },
              {
                "fixed": "4.4.15"
              }
            ]
          },
          "events": [
            {
              "introduced": "69e14246b838443985a541e97327494b8d2fdffb"
            },
            {
              "fixed": "7c28ff90fcb7be07f8fec76f5cdbf4e094917f70"
            }
          ],
          "repo": "https://github.com/mastodon/mastodon",
          "type": "GIT"
        },
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "0"
              },
              {
                "fixed": "4.3.21"
              }
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "8fb494ba0adf87abeb2954cff214118324186edf"
            }
          ],
          "repo": "https://github.com/mastodon/mastodon",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-xqw8-4j56-5hj6"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-601"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33868.json"
  },
  "details": "Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.5.8, 4.4.15, and 4.3.21, an unauthenticated Open Redirect vulnerability (CWE-601) exists in the `/web/*` route due to improper handling of URL-encoded path segments. An attacker can craft a specially encoded URL that causes the application to redirect users to an arbitrary external domain, enabling phishing attacks and potential OAuth credential theft. The issue occurs because URL-encoded slashes (`%2F`) bypass Rails path normalization and are interpreted as host-relative redirects. Versions 4.5.8, 4.4.15, and 4.3.21 patch the issue.",
  "id": "CVE-2026-33868",
  "modified": "2026-04-01T23:09:37.320407822Z",
  "published": "2026-03-27T19:50:07.687Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33868.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/mastodon/mastodon/security/advisories/GHSA-xqw8-4j56-5hj6"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33868"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mastodon has a GET-Based Open Redirect via '/web/%2F\u003cdomain\u003e'"
}