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.
Scoring
- Severity
- MEDIUM
- CVSS base score
- 6.1
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- EPSS probability
- 0.52%
- CWE
- CWE-79, CWE-444, CWE-601
- Published
- 2026-08-19
- Last modified
- 2026-08-21
Affected products
- ether etherpad