{"id":"CVE-2026-33868","state":"PUBLISHED","title":"Mastodon has a GET-Based Open Redirect via '/web/%2F<domain>'","description":"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.","publishedAt":"2026-03-27T19:50:07.687Z","updatedAt":"2026-03-31T18:54:24.919Z","severity":{"score":4.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["mastodon mastodon"],"affected":[{"vendor":"mastodon","product":"mastodon","versions":[{"version":">= 4.5.0, < 4.5.8","status":"affected"},{"version":">= 4.4.0, < 4.4.15","status":"affected"},{"version":"< 4.3.21","status":"affected"}]}],"references":["https://github.com/mastodon/mastodon/security/advisories/GHSA-xqw8-4j56-5hj6"],"weaknesses":["CWE-601"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/33xxx/CVE-2026-33868.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-33868","state":"PUBLISHED","datePublished":"2026-03-27T19:50:07.687Z","dateUpdated":"2026-03-31T18:54:24.919Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-24T15:10:05.678Z"},"containers":{"cna":{"title":"Mastodon has a GET-Based Open Redirect via '/web/%2F<domain>'","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"mastodon","product":"mastodon","versions":[{"version":">= 4.5.0, < 4.5.8","status":"affected"},{"version":">= 4.4.0, < 4.4.15","status":"affected"},{"version":"< 4.3.21","status":"affected"}]}],"references":[{"url":"https://github.com/mastodon/mastodon/security/advisories/GHSA-xqw8-4j56-5hj6","name":"https://github.com/mastodon/mastodon/security/advisories/GHSA-xqw8-4j56-5hj6","tags":["x_refsource_CONFIRM"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":4.3,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-601","lang":"en","description":"CWE-601: URL Redirection to Untrusted Site ('Open Redirect')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-27T19:50:07.687Z"},"source":{"advisory":"GHSA-xqw8-4j56-5hj6","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-03-31T18:50:44.597749Z","id":"CVE-2026-33868","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-03-31T18:54:24.919Z"}}]}}}