{"id":"CVE-2026-62367","aliases":["GHSA-xv7q-fvmc-jx96","GO-2026-6758"],"url":"https://o3.security/vulnerability/CVE-2026-62367","summary":"Vikunja: OIDC email-fallback account linking ignores email_verified, enabling local-account takeover","details":"## Summary\n\nWith the per-provider OIDC `emailfallback` option enabled, Vikunja links an SSO login to a pre-existing **local** (username+password) account using only the `email` claim — no `email_verified` (or Microsoft `xms_edov`) check and no password check, on the unauthenticated callback. An attacker who can make the configured issuer emit a token bearing a victim's email logs in as that victim with a full session and no victim interaction (the nOAuth / Grafana CVE-2023-3128 class). The 2.3.0 fix for GHSA-8jvc-mcx6-r4cg added a TOTP gate, not an `email_verified` gate, so users without TOTP remain exposed.\n\n## Details\n\nReferences are `pkg/modules/auth/openid/openid.go` at HEAD. Identity is first resolved on the immutable `(issuer, subject)` pair (`openid.go:428`). On a subject miss with `emailfallback` on, `fallbackSearchUsers` adds an email-only lookup against local accounts:\n\n```go\n// openid.go:413\nsearches = append(searches, &user.User{Issuer: user.IssuerLocal, Email: cl.Email})\n```\n\n`getUser` resolves this via `s.Get()`, which ANDs non-zero fields -> `WHERE issuer='local' AND email=?`. Local users always have `Issuer=\"local\"` (`user_create.go:38`), so the lookup matches any local account by email alone; `getOrCreateUser` returns it and the caller mints a session — the password is never read. The `claims` struct has no `email_verified` field (`openid.go:80`) and `getClaims` never consults one; a repo-wide grep for `email_verified`/`xms_edov` returns nothing. The code already warns about this at `openid.go:388` (\"Discouraged for untrusted providers where someone can set email without verification\") — but enforces nothing.\n\n## Impact\n\nUnauthenticated takeover of any existing **local** account (read/write/delete its projects, tasks, attachments, shares), bypassing the password. Scope notes: only `issuer='local'` accounts are matched (not pure-SSO users); the attacker's `sub` is not bound to the victim record, but the attack is repeatable; TOTP users are protected by the 2.3.0 `enforceTOTPIfRequired` gate (`openid.go:250`), non-TOTP users are not.\n\n## Preconditions\n\n1. Admin enabled `emailfallback: true` (defaults false — a default install is unaffected).\n2. The configured issuer lets the attacker assert the victim's unverified email: a self-service IdP (Keycloak/Authentik/Auth0/Dex with editable email), a mixed federation, or a multi-tenant Entra `/common` app. `iss`/`aud` are pinned, but the attacker controls `email`, not the issuer.\n3. The victim has a local account.\n\nNot reachable against a single-tenant IdP that verifies email and disallows self-set addresses.\n\n## Recommended Fix\n\nAdd `email_verified` to the `claims` struct and require it `true` on the email-fallback branch before linking to a local account; reject when absent/false. For Entra also require `xms_edov` and pin multi-tenant configs to an allowed-tenant list. Fail closed on an email collision not backed by a verified email from a trusted single-tenant issuer rather than silently logging the caller in.","published":"2026-10-09T20:49:08.891Z","modified":"2026-10-24T02:30:35.347703927Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Go","name":"code.vikunja.io/api","fixedVersion":"2.4.0"}],"fix":{"url":"https://github.com/go-vikunja/vikunja/commit/7854f2729ab72000210b61c25929678fd6901630","label":"go-vikunja/vikunja@7854f27"},"references":[{"type":"WEB","url":"https://github.com/go-vikunja/vikunja/releases/tag/v2.4.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/62xxx/CVE-2026-62367.json"},{"type":"ADVISORY","url":"https://github.com/go-vikunja/vikunja/security/advisories/GHSA-xv7q-fvmc-jx96"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-62367"},{"type":"FIX","url":"https://github.com/go-vikunja/vikunja/commit/7854f2729ab72000210b61c25929678fd6901630"},{"type":"PACKAGE","url":"https://github.com/go-vikunja/vikunja"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-24T02:30:35.347703927Z"}}