{"id":"CVE-2026-33868","summary":"Mastodon has a GET-Based Open Redirect via '/web/%2F\u003cdomain\u003e'","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.","aliases":["BIT-mastodon-2026-33868","GHSA-xqw8-4j56-5hj6"],"modified":"2026-04-10T05:42:56.985504Z","published":"2026-03-27T19:50:07.687Z","database_specific":{"cwe_ids":["CWE-601"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33868.json","cna_assigner":"GitHub_M"},"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mastodon/mastodon","events":[{"introduced":"26c78392f88afccebb8a88b68bc9994a9ce12648"},{"fixed":"38e7bb9b866b5d207a511de093de25536f13e9c4"}],"database_specific":{"versions":[{"introduced":"4.5.0"},{"fixed":"4.5.8"}]}},{"type":"GIT","repo":"https://github.com/mastodon/mastodon","events":[{"introduced":"69e14246b838443985a541e97327494b8d2fdffb"},{"fixed":"7c28ff90fcb7be07f8fec76f5cdbf4e094917f70"}],"database_specific":{"versions":[{"introduced":"4.4.0"},{"fixed":"4.4.15"}]}},{"type":"GIT","repo":"https://github.com/mastodon/mastodon","events":[{"introduced":"0"},{"fixed":"8fb494ba0adf87abeb2954cff214118324186edf"}],"database_specific":{"versions":[{"introduced":"0"},{"fixed":"4.3.21"}]}}],"versions":["v0.1.0","v0.1.1","v0.1.2","v0.6","v0.7","v0.8","v0.9","v0.9.9","v1.0","v1.1","v1.1.1","v1.1.2","v1.2","v1.2.1","v1.2.2","v1.3","v1.3.1","v1.3.2","v1.4.1","v1.4.2","v1.4.3","v1.4.4","v1.4.5","v1.4.6","v1.4.7","v1.4rc1","v1.4rc2","v1.4rc3","v1.4rc4","v1.4rc5","v1.4rc6","v1.5.0","v1.5.0rc1","v1.5.0rc2","v1.5.0rc3","v1.5.1","v1.6.0","v1.6.0rc1","v1.6.0rc2","v1.6.0rc3","v1.6.0rc4","v1.6.0rc5","v1.6.1","v2.0.0","v2.0.0rc1","v2.0.0rc2","v2.0.0rc3","v2.0.0rc4","v2.1.0","v2.1.0rc1","v2.1.0rc2","v2.1.0rc3","v2.1.0rc4","v2.1.0rc5","v2.1.0rc6","v2.1.1","v2.1.2","v2.1.3","v2.2.0","v2.2.0rc1","v2.2.0rc2","v2.3.0","v2.3.0rc1","v2.3.0rc2","v2.3.0rc3","v2.3.1","v2.3.1rc1","v2.3.1rc2","v2.3.1rc3","v2.3.2","v2.3.2rc1","v2.3.2rc2","v2.3.2rc3","v2.3.2rc4","v2.3.2rc5","v2.4.0","v2.4.0rc1","v2.4.0rc2","v2.4.0rc3","v2.4.0rc4","v2.4.0rc5","v2.4.1","v2.4.1rc1","v2.4.1rc2","v2.4.1rc3","v2.4.1rc4","v2.4.2","v2.4.2rc1","v2.4.2rc2","v2.4.2rc3","v2.4.3","v2.4.3rc1","v2.4.3rc2","v2.4.3rc3","v2.5.0","v2.5.0rc1","v2.5.0rc2","v2.6.0","v2.6.0rc1","v2.6.0rc2","v2.6.0rc3","v2.6.0rc4","v2.6.1","v2.7.0","v2.7.0rc1","v2.7.0rc2","v2.7.0rc3","v2.7.1","v2.8.0","v2.8.0rc1","v2.8.0rc2","v2.8.0rc3","v2.8.1","v2.8.2","v2.9.0","v2.9.0rc1","v2.9.0rc2","v2.9.1","v2.9.2","v3.0.0","v3.0.0rc1","v3.0.0rc2","v3.0.0rc3","v3.0.1","v3.1.0","v3.1.0rc1","v3.1.0rc2","v3.1.1","v3.1.2","v3.1.3","v3.1.4","v3.2.0","v3.2.0rc1","v3.2.0rc2","v3.3.0","v3.3.0rc1","v3.3.0rc2","v3.3.0rc3","v3.4.0","v3.4.0rc1","v3.4.0rc2","v3.4.1","v3.5.0","v3.5.0rc1","v3.5.0rc2","v3.5.0rc3","v3.5.1","v3.5.2","v3.5.3","v4.0.0","v4.0.0rc1","v4.0.0rc2","v4.0.0rc3","v4.0.0rc4","v4.0.1","v4.0.2","v4.1.0","v4.1.0rc1","v4.1.0rc2","v4.1.0rc3","v4.2.0","v4.2.0-beta1","v4.2.0-beta2","v4.2.0-beta3","v4.2.0-rc1","v4.2.0-rc2","v4.3.0","v4.3.0-beta.1","v4.3.0-beta.2","v4.3.0-rc.1","v4.3.1","v4.3.10","v4.3.11","v4.3.12","v4.3.13","v4.3.14","v4.3.15","v4.3.16","v4.3.17","v4.3.18","v4.3.19","v4.3.2","v4.3.20","v4.3.3","v4.3.4","v4.3.5","v4.3.6","v4.3.7","v4.3.8","v4.3.9","v4.4.0","v4.4.1","v4.4.10","v4.4.11","v4.4.12","v4.4.13","v4.4.14","v4.4.2","v4.4.3","v4.4.4","v4.4.5","v4.4.6","v4.4.7","v4.4.8","v4.4.9","v4.5.0","v4.5.1","v4.5.2","v4.5.3","v4.5.4","v4.5.5","v4.5.6","v4.5.7"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33868.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"}]}