Summary
Vikunja: OIDC email-fallback account linking ignores email_verified, enabling local-account takeover
With 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.
Details
References 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:
// openid.go:413
searches = append(searches, &user.User{Issuer: user.IssuerLocal, Email: cl.Email})
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.
Preconditions
- Admin enabled
emailfallback: true(defaults false, a default install is unaffected). - 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
/commonapp.iss/audare pinned, but the attacker controlsemail, not the issuer. - The victim has a local account.
Not reachable against a single-tenant IdP that verifies email and disallows self-set addresses.
Impact
Unauthenticated 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.
The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Add 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.
Frequently Asked Questions
- What is CVE-2026-62367? CVE-2026-62367 is a high-severity improper authentication vulnerability in code.vikunja.io/api (go), affecting versions >= 1.0.0, <= 2.3.0. It is fixed in 2.4.0. The application does not adequately verify the identity of a user, device, or process before granting access.
- Which versions of code.vikunja.io/api are affected by CVE-2026-62367? code.vikunja.io/api (go) versions >= 1.0.0, <= 2.3.0 is affected.
- Is there a fix for CVE-2026-62367? Yes. CVE-2026-62367 is fixed in 2.4.0. Upgrade to this version or later.
- Is CVE-2026-62367 exploitable, and should I be worried? Whether CVE-2026-62367 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-62367 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-62367? Upgrade
code.vikunja.io/apito 2.4.0 or later.