Vulnerability · Published Oct 30, 2026 · Assigned by GitHub_M
CVE-2026-48164Collabora Online: Reflected HTML injection through host_session_id
Medium 4.7
In plain English
A medium-severity cross-site scripting in online from CollaboraOnline. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| CollaboraOnline | online | < 24.04.18>= 25.04.0-0, < 25.04.11 |
Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N