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

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Summary

CVECVE-2026-55210
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-21 22:16:56 UTC
Updated2026-09-23 18:30:42 UTC
DescriptionJoplin 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.

Risk And Classification

Primary CVSS: v3.1 7.4 HIGH from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS: 0.004790000 probability, percentile 0.386670000 (date 2026-09-24)

Problem Types: CWE-290 | CWE-290 CWE-290: Authentication Bypass by Spoofing

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
3.1CNADECLARED7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Laurent22 Joplin affected < 3.7.2 Not specified

References

ReferenceSourceLinkTags
github.com/laurent22/joplin/pull/15647 [email protected] github.com
github.com/laurent22/joplin/security/advisories/GHSA-5px3-4f5x-hjc5 [email protected] github.com
github.com/laurent22/joplin/commit/b6d69d072919cbe769234f93d95ed21e1ec129b2 [email protected] github.com
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