{"id":"CVE-2020-15233","aliases":["GHSA-rfq3-w54c-f9q5"],"url":"https://o3.security/vulnerability/CVE-2020-15233","summary":"OAuth2 Redirect URL validity does not respect query parameters and character casing for loopback addresses","details":"### Impact\n\n[fosite#400](https://github.com/ory/fosite/pull/400) (released as v0.30.2) introduced a new feature for handling redirect URLs pointing to loopback interfaces ([rfc8252#section-7.3](https://tools.ietf.org/html/rfc8252#section-7.3)). As part of that change new behavior was introduced which failed to respect the redirect URL's (only for loopback interfaces!) query parameters\n\n1. Registering a client with allowed redirect URL `http://127.0.0.1/callback`\n2. Performing OAuth2 flow and requesting redirect URL `http://127.0.0.1/callback?bar=foo`\n3. Instead of an error, the browser is redirected to `http://127.0.0.1/callback?bar=foo` with a potentially successful OAuth2 response.\n\nas well as the host parameter (as long as the host is a loopback interface):\n\n1. Registering a client with allowed redirect URL `https://example.com/callback`\n2. Performing OAuth2 flow and requesting redirect URL `http://127.0.0.1/callback`\n3. Instead of an error, the browser is redirected to `http://127.0.0.1/callback` with a potentially successful OAuth2 response.\n\nThese bugs are only applicable in scenarios where the attacker has control over the loopback interface (`localhost`, `127.0.0.1`, `[::1]`) where the browser performing the OAuth2 flow is running.","published":"2020-10-02T21:15:12.403Z","modified":"2026-07-09T02:49:28.871135Z","cvss":{"score":4.8,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Go","name":"github.com/ory/fosite","fixedVersion":"0.34.1"}],"fix":{"url":"https://github.com/ory/fosite/commit/cdee51ebe721bfc8acca0fd0b86b030ca70867bf","label":"ory/fosite@cdee51e"},"references":[{"type":"ADVISORY","url":"https://github.com/ory/fosite/security/advisories/GHSA-rfq3-w54c-f9q5"},{"type":"FIX","url":"https://github.com/ory/fosite/commit/cdee51ebe721bfc8acca0fd0b86b030ca70867bf"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2020-15233"},{"type":"WEB","url":"https://github.com/ory/fosite/pull/400"},{"type":"PACKAGE","url":"https://github.com/ory/fosite"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T02:49:28.871135Z"}}