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CVE-2026-55089— Etherpad: JWT `admin` claim presence-only check lets non-admin OAuth users invoke every Etherpad HTTP API endpoint

Quick assessment

Affected
ether etherpad
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

etherpad是ETHER组织的一个支持多人实时在线协作的文档编辑工具。 ETHER etherpad 2.1.0版本至3.1.0之前版本存在授权问题漏洞，该漏洞源于APIHandler.ts在OAuth授权码路径中使用requiredClaims验证admin声明时仅检查声明存在，非管理员用户可利用有效签名令牌调用管理功能（如setHTML、setText、deletePad等），导致跨实例泄露、修改或删除pads。

CVSS 9.9 · Critical EPSS 0.36% · P28

Affected Version Matrix 1

VendorProduct Version RangeStatus
ether etherpad >= 2.1.0, < 3.1.0 affected
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I. Basic Information for CVE-2026-55089

Vulnerability Information
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Vulnerability Title
Etherpad: JWT `admin` claim presence-only check lets non-admin OAuth users invoke every Etherpad HTTP API endpoint
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5
Vulnerability Title
ETHER etherpad 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
etherpad是ETHER组织的一个支持多人实时在线协作的文档编辑工具。 ETHER etherpad 2.1.0版本至3.1.0之前版本存在授权问题漏洞，该漏洞源于APIHandler.ts在OAuth授权码路径中使用requiredClaims验证admin声明时仅检查声明存在，非管理员用户可利用有效签名令牌调用管理功能（如setHTML、setText、deletePad等），导致跨实例泄露、修改或删除pads。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ether etherpad >= 2.1.0, < 3.1.0 -

II. Public POCs for CVE-2026-55089

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 7365 chars
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III. Intelligence Information for CVE-2026-55089

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Patches & Fixes for CVE-2026-55089 (1)

Vendor Advisories for CVE-2026-55089 (1)

Vendor Pages for CVE-2026-55089 (1)

Same Patch Batch · ether · 2026-08-19 · 6 CVEs total

CVE-2026-55085 9.6 CRITICAL Etherpad: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripti
CVE-2026-55088 6.8 MEDIUM Etherpad: Device-to-device author-token transfer endpoint is replayable, never expires, an
CVE-2026-55087 6.1 MEDIUM Etherpad: x-proxy-path header reflected into admin HTML/JS/CSS (cache-poisoning XSS) and c
CVE-2026-55090 5.3 MEDIUM Etherpad: Stored XSS in HTML export via unescaped attribute-pool values
CVE-2026-55086 4.2 MEDIUM Etherpad: Import/export use Math.random() for temp file paths; predictable paths on shared

IV. Related Vulnerabilities

Same product: etherpad
Same vendor: ether
Same weakness: CWE-863

V. Comments for CVE-2026-55089

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