Joplin: SAML SSO account takeover via email-based account linking (missing is_external check in ssoLogin)

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.

Scores

EPSS (exploitation in 30 days)

0.48% · top 58% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: total

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.4.

Weakness

• CWE-290: Authentication Bypass by Spoofing (opens in a new tab)All about CWE-290 and its CVEs

Affected products

• laurent22 · joplin

  • affected < 3.7.2

References (3)

• https://github.com/laurent22/joplin/security/advisories/GHSA-5px3-4f5x-hjc5 (opens in a new tab)x_refsource_CONFIRM
• https://github.com/laurent22/joplin/pull/15647 (opens in a new tab)x_refsource_MISC
• https://github.com/laurent22/joplin/commit/b6d69d072919cbe769234f93d95ed21e1ec129b2 (opens in a new tab)x_refsource_MISC

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-55210](https://trackcve.app/badge/CVE-2026-55210.svg)](https://trackcve.app/cve/CVE-2026-55210)

Record last updated 22 Sept 2026, 13:07 UTC.