{"id":"BIT-mastodon-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":["CVE-2026-33868","GHSA-xqw8-4j56-5hj6"],"modified":"2026-09-08T08:48:12.910137974Z","published":"2026-03-31T08:45:35.531Z","database_specific":{"cpes":["cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*"],"severity":"Medium"},"references":[{"type":"ADVISORY","url":"https://github.com/mastodon/mastodon/security/advisories/GHSA-xqw8-4j56-5hj6"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33868"}],"affected":[{"package":{"name":"mastodon","ecosystem":"Bitnami","purl":"pkg:bitnami/mastodon"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.3.21"},{"introduced":"4.4.0"},{"fixed":"4.4.15"},{"introduced":"4.5.0"},{"fixed":"4.5.8"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/mastodon/BIT-mastodon-2026-33868.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"}]}],"schema_version":"1.9.0"}