{"id":"CVE-2020-15233","aliases":["GHSA-rfq3-w54c-f9q5"],"title":"OAuth2 Redirect URL validity does not respect query parameters and character casing for loopback addresses","summary":"OAuth2 Redirect URL validity does not respect query parameters and character casing for loopback addresses","severity":"medium","cvss":6.1,"cvssVector":"CVSS:3.0/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N/E:P/RL:O/RC:C","vendor":"ory","product":"github.com/ory/fosite","ecosystem":"go","affected":["github.com/ory/fosite >= 0.30.3, < 0.34.1"],"patched":["github.com/ory/fosite 0.34.1"],"published":"2021-05-24","updated":"2026-07-08","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-rfq3-w54c-f9q5","references":[{"url":"https://github.com/ory/fosite/security/advisories/GHSA-rfq3-w54c-f9q5"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-15233"},{"url":"https://github.com/ory/fosite/pull/400"},{"url":"https://github.com/ory/fosite/commit/cdee51ebe721bfc8acca0fd0b86b030ca70867bf"},{"url":"https://github.com/ory/fosite"}],"tags":["osv","go"],"epss":0.008,"epssPercentile":0.55036,"ingestedAt":"2026-07-09T18:56:36.902Z","slug":"CVE-2020-15233","body":"## Overview\n\n### 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.\n\n## Affected packages\n\n- `github.com/ory/fosite >= 0.30.3, < 0.34.1`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `github.com/ory/fosite 0.34.1`","depth":"sunlit","depthScore":34,"depthScoreParts":{"impact":33.6,"likelihood":0.2,"exploitation":0,"ransomware":0},"changes":[]}