CVE-2026-55087
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Summary
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.
Affected Software
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| ether | etherpad | >= 2.1.0, < 3.1.0 | affected |
Weaknesses
- CWE-79: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CWE-444: CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
- CWE-601: CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
References
- https://github.com/ether/etherpad/security/advisories/GHSA-fjgc-3mj7-8rg8
- https://github.com/ether/etherpad/pull/7784
- https://github.com/ether/etherpad/commit/8c6104c5d5daf41f0d454acc04d42dffa0e0d996
- https://github.com/ether/etherpad/tree/3.1.0
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