Vikunja: OIDC email-fallback account linking ignores email_verified, enabling local-account takeover

Vikunja is an open-source self-hosted task management platform. In versions 1.0.0 through 2.3.0, when an administrator enables the per-provider `emailfallback` option on an OpenID Connect provider, Vikunja links an SSO login to a pre-existing local (username+password) account using only the `email` claim from the IdP. The fallback never checks an `email_verified` (or Microsoft `xms_edov`) signal and never requires the matched account's password. An attacker who can obtain a token from the configured issuer carrying a victim's email logs in as that victim with a full session, with no consent or interaction from the victim. Version 2.4.0 fixes the issue.

Source published

9 Oct 2026 20:49:08 UTC

Source modified

13 Oct 2026 20:25:26 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 4.0 · 7.5 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