{"id":"GHSA-c5c4-8r6x-56w3","summary":"OAuth2 Proxy has an Authorization Bypass in Email Domain Validation via Malformed Multi-@ Email Claims","details":"### Impact\n\nAn authorization bypass exists in OAuth2 Proxy as part of the `email_domain` enforcement option. An attacker may be able to authenticate with an email claim such as `attacker@evil.com@company.com` and satisfy an allowed domain check for `company.com`, even though the claim is not a valid email address.\n\nThe issue **ONLY** affects deployments that rely on `email_domain` restrictions and accept email claim values from identity providers or claim mappings that do not strictly enforce normal email syntax. The practical risk ONLY exists in self-hosted or custom OIDC environments and federated setups where unexpected claim values can reach oauth2-proxy. Standard hosted providers that enforce valid email formatting ARE NOT effected.\n\n### Patches\nUsers should upgrade to `v7.15.2` or later once available.\n\n### Workarounds\nThe most effective workaround is to ensure the configured identity provider cannot emit malformed or attacker-controlled email claim values.","aliases":["BIT-oauth2-proxy-2026-40574","CVE-2026-40574","GO-2026-5314"],"modified":"2026-07-21T13:56:41Z","published":"2026-04-15T19:23:54Z","database_specific":{"cwe_ids":["CWE-863"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-04-15T19:23:54Z","nvd_published_at":"2026-04-21T17:16:55Z"},"references":[{"type":"WEB","url":"https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-c5c4-8r6x-56w3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40574"},{"type":"PACKAGE","url":"https://github.com/oauth2-proxy/oauth2-proxy"}],"affected":[{"package":{"name":"github.com/oauth2-proxy/oauth2-proxy/v7","ecosystem":"Go","purl":"pkg:golang/github.com/oauth2-proxy/oauth2-proxy/v7"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"7.15.2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-c5c4-8r6x-56w3/GHSA-c5c4-8r6x-56w3.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N"}]}