CVE-2026-55090: Ep etherpad lite Cross-Site Scripting Vulnerability

HIGH
Advisory Identifier: GHSA-2jp7-wwpg-3p9w
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CWE-79
Published
Advisory Summary

CVE-2026-55090 is a HIGH cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Ep etherpad lite libraries in the npm ecosystem. The issue involves etherpad has stored xss in html export via unescaped attribute-pool values. Remediation is available by upgrading affected packages to version 3.3.0.

CVE-2026-55090 at a Glance

CVE Identifier CVE-2026-55090
GHSA Identifier GHSA-2jp7-wwpg-3p9w
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Ep etherpad lite
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-55090

To remediate this vulnerability, upgrade all affected Ep etherpad lite dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

ep_etherpad-lite fixed: 3.3.0 
npm install ep_etherpad-lite@3.3.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls ep_etherpad-lite

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-55090, inspect your project dependencies using npm:

npm ls ep_etherpad-lite

Analyze the terminal output to locate any version of Ep etherpad lite in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.3.0), your application is affected.

Note: The npm ls ep_etherpad-lite command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Ep etherpad lite, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Fix: PR #7905 (ether/etherpad). `getHTMLFromAtext` in `src/node/utils/ExportHtml.ts` interpolates values from the `exportHtmlAdditionalTagsWithData` plugin hook into `span data-<k>="<v>"` without HTML-attribute escaping. The value comes verbatim from the pad attribute pool, which a pad editor controls via a crafted changeset (only `author` attributes are validated; `moveOpsToNewPool` -> `AttributePool.putAttrib` stores any value). With a bundled plugin that registers the hook (ep_font_color / ep_font_size), an attribute value such as `" onload="alert(1)` is exported as `<span data-color="" onload="alert(1)">` and served as text/html, yielding stored XSS for any collaborator who opens the export. Fix: escape the name and value via `Security.escapeHTMLAttribute`. PR #7905 also adds a startup warning when default/placeholder account or SSO credentials are configured (defense-in-depth, non-breaking).

CVE-2026-55090 Affected Ep etherpad lite Versions

1 component(s)
Fixed Versions:
3.3.0
Product / Package Ecosystem Affected Versions Fixed Version
ep_etherpad-lite
npm/ep_etherpad-lite
npm
< 3.3.0
3.3.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/ether/etherpad/security/advisories/GHSA-2jp7-wwpg-3p9w
Ep etherpad lite Source Repository REPOSITORY
https://github.com/ether/etherpad/pull/7905
Security Fix Commit FIX COMMIT
https://github.com/ether/etherpad/commit/86c56cf827dd6e5ff1b6cd3760f87adc47f58bb1
Ep etherpad lite Source Repository REPOSITORY
https://github.com/ether/etherpad
Ep etherpad lite Release RELEASE
https://github.com/ether/etherpad/releases/tag/3.3.0

Frequently Asked Questions

What is CVE-2026-55090?
CVE-2026-55090 is a security vulnerability in Ep etherpad lite involving Etherpad has stored XSS in HTML export via unescaped attribute-pool values under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Ep etherpad lite versions are affected?
Affected versions include releases prior to 3.3.0 across affected packages: ep_etherpad-lite.
What version fixes CVE-2026-55090?
Upgrading to 3.3.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is ep_etherpad-lite affected?
Yes, ep_etherpad-lite is affected in releases prior to 3.3.0. Upgrade your dependency to 3.3.0 or later.
What CWE is associated with CVE-2026-55090?
CVE-2026-55090 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check npm dependencies for CVE-2026-55090?
Run the dependency tree command: 'npm ls ep_etherpad-lite'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2jp7-wwpg-3p9w",
  "modified" : "2026-08-17T17:49:39Z",
  "published" : "2026-08-17T17:49:38Z",
  "aliases" : [ "CVE-2026-55090" ],
  "summary" : "Etherpad has stored XSS in HTML export via unescaped attribute-pool values",
  "details" : "Fix: PR #7905 (ether/etherpad).\n\n`getHTMLFromAtext` in `src/node/utils/ExportHtml.ts` interpolates values from the `exportHtmlAdditionalTagsWithData` plugin hook into `span data-<k>=\"<v>\"` without HTML-attribute escaping. The value comes verbatim from the pad attribute pool, which a pad editor controls via a crafted changeset (only `author` attributes are validated; `moveOpsToNewPool` -> `AttributePool.putAttrib` stores any value). With a bundled plugin that registers the hook (ep_font_color / ep_font_size), an attribute value such as `\" onload=\"alert(1)` is exported as `<span data-color=\"\" onload=\"alert(1)\">` and served as text/html, yielding stored XSS for any collaborator who opens the export.\n\nFix: escape the name and value via `Security.escapeHTMLAttribute`. PR #7905 also adds a startup warning when default/placeholder account or SSO credentials are configured (defense-in-depth, non-breaking).",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "ep_etherpad-lite"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.3.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.8.14"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/ether/etherpad/security/advisories/GHSA-2jp7-wwpg-3p9w"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ether/etherpad/pull/7905"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ether/etherpad/commit/86c56cf827dd6e5ff1b6cd3760f87adc47f58bb1"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ether/etherpad"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ether/etherpad/releases/tag/3.3.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-17T17:49:38Z",
    "nvd_published_at" : null
  }
}