CVE-2026-55210 Joplin: SAML SSO account takeover via email-based account linking (missing is_external check in ssoLogin)
Attackers can take over local Joplin accounts via SAML SSO by exploiting missing external account checks in mixed authentication deployments.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-55210?
CVE-2026-55210 is a high-severity authentication bypass vulnerability in laurent22 joplin, published on 21 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Joplin is an open source note-taking and to-do application that organises notes and lists into notebooks. Prior to 3.7.2, Joplin Server's UserModel.ssoLogin() returns an existing account matched by an IdP-asserted email without checking the account's is_external flag. In deployments using mixed local and SAML authentication, an attacker whose IdP session can assert a local user's email can pass POST /api/saml, receive a session for that local account, and access or modify the victim's notes, files, and settings without knowing the local password. This issue is fixed in version 3.7.2.
Weakness: CWE-290
Which versions are affected by CVE-2026-55210?
How do I fix CVE-2026-55210?
No fix has been published for CVE-2026-55210 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-55210 being exploited?
There is no known exploitation of CVE-2026-55210 in the wild and no public exploit code.
Sources
Also known as GHSA-5px3-4f5x-hjc5.