Vulnerability in CollaboraOnline online

[ Description ]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.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• BSI CERT-Bund1 Nov 2026WID-SEC-2026-4272

  Collabora Online: Multiple vulnerabilities Translated from German

  CVE-2026-48164CVE-2026-46499

[ References ]References

• github.com/CollaboraOnline/online/commit/2d4469d27f0c52f4b28b64090e60452d2e147279
• github.com/CollaboraOnline/online/security/advisories/GHSA-wgmm-q3ch-64jj