ep_etherpad-lite: Cache-poisoning Cross-site Scripting and Open Redirect via x-proxy-path Header

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-55087: 0.58% estimated exploitation activity in the next 30 days; percentile 47.67 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

GHSA-03 — x-proxy-path header reflected into admin HTML/JS/CSS (cache-poisoning XSS) and concatenated into redirect (open-redirect) Severity: Medium CVSS v3.1 vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N CVSS suggested base score: ~6.1 — Medium (Re-validate in the first.gov calculator before filing. Score depends heavily on whether you assume a cooperative cache exists in front of the deployment — single-origin admin-only ops with no shared cache push toward 4.x; cache-poisoning against a CDN pushes toward 7.x.) CWE: CWE-79 Improper Neutralization of Input During Web Page Generation, CWE-601 URL Redirection to Untrusted Site, CWE-444 Inconsistent Interpretation of HTTP Requests Title x-proxy-path request header is interpolated into admin HTML/JS/CSS without sanitisation (cache-poisoning XSS) and into a /p/:pad/timeslider redirect target (open-redirect via protocol-relative URL) Description Etherpad lets operators run behind a reverse proxy that prefixes every route with a…

Published by the source

13 Aug 2026, 13:46 UTC

Last modified by the source

13 Aug 2026, 13:46 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fjgc-3mj7-8rg8

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-55087

Advisory: ep_etherpad-lite: Cache-poisoning Cross-site Scripting and Open Redirect via x-proxy-path Header
IDs: CVE-2026-55087, GHSA-fjgc-3mj7-8rg8
Record: https://patchnext.com/advisories/cve-2026-55087 (revision 1, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ep_etherpad-lite 3.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm ep_etherpad-lite: affected >= 2.1.0, <= 3.0.0; fixed in 3.1.0

## Suggested inspection (read-only)
- `npm ls ep_etherpad-lite --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ep_etherpad-lite.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-fjgc-3mj7-8rg8 (GitHub-reviewed advisory GHSA-fjgc-3mj7-8rg8 lists affected ranges: npm ep_etherpad-lite >=2.1.0 <=3.0.0)

Commands are suggestions: review each one before running it.