Vulnerability Description
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 Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/ether/etherpad/commit/8c6104c5d5daf41f0d454acc04d42dffa0e0d99
- 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
FAQ
What is CVE-2026-55087?
CVE-2026-55087 is a vulnerability with a CVSS score of 6.1 (MEDIUM). 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 ...
How severe is CVE-2026-55087?
CVE-2026-55087 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-55087?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.