{"id":"GHSA-xv7q-fvmc-jx96","revision":"c441b51eb6eb4e9e8f19260a7040ac18","records":[{"revision":"c441b51eb6eb4e9e8f19260a7040ac18","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-xv7q-fvmc-jx96","aliases":["CVE-2026-62367","GO-2026-6758"],"title":"Vikunja: OIDC email-fallback account linking ignores email_verified, enabling local-account takeover","description":"## 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.","state":0,"publishedAt":"2026-10-09T20:49:06+00:00","modifiedAt":"2026-10-19T21:40:54.2886837+00:00","affected":[{"ecosystem":"Go","name":"code.vikunja.io/api","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"1.0.0"},{"kind":"fixed","version":"2.4.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V4","vector":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"HIGH"}],"references":["https://github.com/go-vikunja/vikunja/security/advisories/GHSA-xv7q-fvmc-jx96","https://github.com/go-vikunja/vikunja/commit/7854f2729ab72000210b61c25929678fd6901630","https://github.com/go-vikunja/vikunja","https://github.com/go-vikunja/vikunja/releases/tag/v2.4.0"],"sourceUrl":"https://github.com/advisories/GHSA-xv7q-fvmc-jx96","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-xv7q-fvmc-jx96","identifiers":["GHSA-xv7q-fvmc-jx96","CVE-2026-62367","GO-2026-6758"]},"retained":false,"historicalAffected":[]}],"coverage":[]}