ether Etherpad up to 3.0.x OAuth2 Provider OAuth2Provider.ts improper authorization

Summaryinfo

A vulnerability classified as critical was found in ether Etherpad up to 3.0.x. The impacted element is an unknown function of the file src/node/security/OAuth2Provider.ts of the component OAuth2 Provider. Executing a manipulation can lead to improper authorization. This vulnerability is registered as CVE-2026-55089. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability classified as critical was found in ether Etherpad up to 3.0.x. This vulnerability affects an unknown function of the file src/node/security/OAuth2Provider.ts of the component OAuth2 Provider. The manipulation with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Etherpad is a real-time collaborative editor. From 2.1.0 until 3.1.0, Etherpad's src/node/handler/APIHandler.ts authorizes requests to /api/2/* in the authorization_code OAuth path by using requiredClaims with the admin claim. This check requires only that the claim exists, while src/node/security/OAuth2Provider.ts issues admin: false for configured non-admin users. A non-admin user with a valid signed token can therefore invoke administrative functions including setHTML, setText, appendText, deletePad, copyPad, movePad, restoreRevision, anonymizeAuthor, listAllPads, and listAuthorsOfPad, allowing disclosure, modification, or deletion of pads across the instance. This issue is fixed in version 3.1.0.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-55089 since 06/16/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1548.002.

Upgrading to version 3.1.0 eliminates this vulnerability.

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Productinfo

Vendor

• ether

Name

• Etherpad

Version

• 3.0

Website

• Product: https://github.com/ether/etherpad/

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