CVE-2026-55087

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.

• CWE-79
• CWE-444
• CWE-601

• https://github.com/ether/etherpad/commit/8c6104c5d5daf41f0d454acc04d42dffa0e0d996
• https://github.com/ether/etherpad/pull/7784
• https://github.com/ether/etherpad/security/advisories/GHSA-fjgc-3mj7-8rg8
• https://github.com/ether/etherpad/tree/3.1.0

Published

Aug 19, 2026

Last Modified

Sep 9, 2026

Status

Deferred

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