---
id: "CVE-2026-48164"
kind: "vulnerability"
aliases: ["CVE-2026-48164"]
title: "Collabora Online: crafted URL injects script into the editor page"
severity: "medium"
cvss: 4.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["collabora-online", "coolwsd", "nextcloud", "package", "self-hosted"]
not_affected_if: ["csp-enforced", "fixed-version", "managed-hosting"]
published_at: "2026-10-30T15:16:52+00:00"
first_seen_at: "2026-10-30T15:31:11+00:00"
updated_at: "2026-10-30T15:33:51+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48164", "first_seen_at": "2026-10-30T15:31:11+00:00"}]
---

# Collabora Online: crafted URL injects script into the editor page

Collabora Online does not HTML-encode the host_session_id parameter when it is placed into the cool.html editor page. An attacker who gets a victim to open a crafted link can run scripts in the Collabora iframe and read the session token and page contents, unless a Content Security Policy blocks it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Collabora Online version (`coolwsd --version` or the package version) against the fixed ranges below.
- Check whether the server or reverse proxy sends a `Content-Security-Policy` header on `cool.html` responses.

## Fix

- Collabora Online `24.04.18` for the 24.04 line
- Collabora Online `25.04.11` for the 25.04 line

## Timeline

- 2026-10-30T15:31:11+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-48164

## From the sources

Collabora Online is a collaborative online office suite based on LibreOffice technology. Prior to 24.04.18 and 25.04.11, the `host_session_id` query/form parameter is substituted into the `cool.html` editor page without HTML encoding, unlike parameters passed through the existing variable-encoding mechanism. An attacker who induces a victim to load a crafted URL can inject HTML and, in the absence of an effective `Content Security Policy`, execute scripts in the Collabora Online iframe's origin, exposing the session authentication token and page contents. A reverse proxy that preserves the `Content Security Policy` header sent by `coolwsd` mitigates the script-execution scenario. This issue is fixed in versions 24.04.18 and 25.04.11.

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