CVE-2026-55087: medium-severity vulnerability in etherpad
Etherpad: x-proxy-path header reflected into admin HTML/JS/CSS (cache-poisoning XSS) and concatenated into redirect (open-redirect)
Published · Updated
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28Vexday Risk Score
Patch soon. It has a working public exploit.
ssvc Attendcvss 6.1epss 0.6%
Etherpad is a real-time collaborative editor. From 2.1.0 until 3.1.0, Etherpad uses the attacker-controlled x-proxy-path request header in src/node/hooks/express/admin.ts when substituting paths into HTML, JavaScript, and CSS under /admin without sanitization, Vary: x-proxy-path, or Cache-Control: private, no-store. A shared proxy or CDN can cache the resulting response and serve attacker-injected script to an administrator. In src/node/hooks/express/specialpages.ts, version 3.0.0 also accepts a protocol-relative x-proxy-path value when constructing the /p/:pad/timeslider redirect, allowing redirection to an attacker-controlled host. The issues are exploitable when the deployment permits client-supplied x-proxy-path headers to reach Etherpad. This issue is fixed in version 3.1.0.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Affected products
ether · etherpadRelated CVEs — etherpad
In the same product, most dangerous first.
CVE-2026-55090MEDIUMEtherpad: Stored XSS in HTML export via unescaped attribute-pool valuesEPSS 0.5%CVE-2026-55085CRITICALEtherpad: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in etherpad-liteEPSS 0.5%CVE-2026-55089CRITICALEtherpad: JWT `admin` claim presence-only check lets non-admin OAuth users invoke every Etherpad HTTP API endpointEPSS 0.5%CVE-2026-55088MEDIUMEtherpad: Device-to-device author-token transfer endpoint is replayable, never expires, and exposes the cleartext author tokenEPSS 0.4%CVE-2026-55086MEDIUMEtherpad: Import/export use Math.random() for temp file paths; predictable paths on shared /tmp enable symlink-based file overwriteEPSS 0.1%