Vulnerability in Collabora Online - Built-in CODE Server

[ Why it matters ]Priority signals

• Critical severity: CVSS 9.2

[ Description ]Official description

Collabora Online Built-in CODE Server before 26.4.303 (richdocumentscode), a Nextcloud app, allows remote code execution, as exploited in the wild in September and October 2026, a different vulnerability than CVE-2025-66208. This is an OS command injection in proxy.php when the CODE server isn't running (e.g., the product was recently restarted). The vulnerability is not present in standalone Collabora Online servers; only this deployment with CODE Server is affected.

[ 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-Bund18 Oct 2026WID-SEC-2026-4011

  Collabora Online Built-in CODE Server (NextCloud): Vulnerability allows arbitrary code execution with user rights Translated from German

  CVE-2026-110447

[ References ]References

• github.com/CollaboraOnline/richdocumentscode/issues/354
• help.nextcloud.com/t/to-collabora-built-in-user-update-asap/250516