CVE-2026-55089
Received Received - Intake

Privilege Escalation in Etherpad via OAuth Admin Claim

Publication date: 2026-08-19

Last updated on: 2026-08-19

Assigner: GitHub, Inc.

Description
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.

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Meta Information

Published
2026-08-19
Last Modified
2026-08-19
Generated
2026-08-20
AI Q&A
2026-08-19
EPSS Evaluated
N/A
NVD
CVE-2026-55089
EUVD
EUVD-2026-62737

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
etherpad etherpad From 2.1.0 (inc) to 3.1.0 (inc)
ether etherpad From 2.1.0 (inc) to 3.1.0 (inc)
ether etherpad 3.1.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-863 The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

Attack-Flow Graph

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Executive Summary

CVE-2026-55089 is a critical authorization bypass in Etherpad versions 2.1.0 to 3.0.0. It allows non-admin OAuth users to gain full administrative access to the Etherpad HTTP API by exploiting a flawed JWT validation check. The software only verifies the existence of an 'admin' claim in the token but does not check its value, permitting tokens with 'admin': false to pass authentication.

Detection Guidance

Check Etherpad version with: npm list etherpad or grep version in package.json. If version is between 2.1.0 and 3.0.0, the system is vulnerable. Review OAuth/JWT configuration files for non-empty settings.users with non-admin entries. Monitor API logs for unauthorized administrative actions like setHTML, deletePad, or listAllPads.

Impact Analysis

This vulnerability allows non-admin users to perform privileged actions such as modifying pad content, deleting pads, copying pads, moving pads, restoring revisions, anonymizing authors, listing all pads, and listing authors of pads. This can lead to unauthorized disclosure, modification, or deletion of sensitive data across the Etherpad instance.

Compliance Impact

This vulnerability could lead to unauthorized access and modification of sensitive data, violating confidentiality and integrity requirements under GDPR and HIPAA. Non-compliance may result in legal penalties, data breach notifications, and reputational damage due to unauthorized exposure or alteration of protected information.

Mitigation Strategies

Upgrade Etherpad to version 3.1.0 or later immediately. If upgrading is not possible, disable OAuth/JWT authentication or restrict access to administrative functions. Review and validate all JWT tokens to ensure the admin claim is explicitly true before processing requests.

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