How to fix CVE-2026-110447: Collabora Online – Built-in CODE Server (exploited in the wild)

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.

• Severity: CRITICAL (CVSS 4.0 9.2, vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N).
• Weakness: CWE-78.
• NVD published 2026-10-14, status Deferred.

Anyone running Collabora Online – Built-in CODE Server. Internet-facing instances are the priority.

NVD has not published affected version ranges for this CVE yet. Use the vendor advisory in the sources below to confirm which builds are affected.

• Exploited in the wild: added to the CISA Known Exploited Vulnerabilities catalog on 2026-10-23; federal remediation due date 2026-10-26.

• EPSS (probability of exploitation activity in the next 30 days): 2.28%, higher than 83% of all scored CVEs (as of 2026-10-24).
• CVERadar threat level: 62/100 (see methodology).
• Likely ATT&CK techniques: T1190 Exploit Public-Facing Application (inferred); T1059 Command and Scripting Interpreter (inferred); T1203 Exploitation for Client Execution (inferred).

1. Find every instance. List where Collabora Online – Built-in CODE Server runs, including test, DR and forgotten internet-facing systems, and record the installed version.
2. Apply the latest vendor update. NVD does not list a fixed version, so follow the vendor advisory for the patched release.
3. If you can't patch today, follow CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
4. Verify the fix. Re-run the version check on every instance and confirm it reports the fixed build. Re-scan from outside if the service is exposed.
5. Hunt for signs of earlier compromise. If the system was exposed before you patched, assume it may have been hit and check the items below.
6. Rotate credentials stored on or used by the affected system if you cannot rule out compromise, and keep the logs you reviewed.

Detection hints

• T1190 Exploit Public-Facing Application: Review WAF, reverse-proxy and application logs for unusual requests to Collabora Online – Built-in CODE Server (odd paths, oversized or encoded payloads, bursts of errors), going back to at least 2026-10-14.
• T1059 Command and Scripting Interpreter: Watch for the service process spawning shells or script interpreters.
• T1203 Exploitation for Client Execution: Exploitation of client or server software usually shows as crashes of the affected process followed by unexpected child processes; check EDR alerts for both.

# Child processes of web/service accounts (look for sh, bash, python, perl, curl, wget)
ps -eo pid,ppid,user,lstart,cmd --forest | grep -E "www-data|apache|nginx|tomcat" -A3

Detection commands are generic starting points, not CVE-specific signatures. Use the indicators from the vendor advisory when it publishes them.

• NVD: CVE-2026-110447 nvd.nist.gov/vuln/detail/CVE-2026-110447
• CVE.org record www.cve.org/CVERecord?id=CVE-2026-110447
• Vendor link from CISA KEV help.nextcloud.com/t/to-collabora-built-in-user-update-asap/250516
• Vendor link from CISA KEV github.com/CollaboraOnline/online/security/advisories/GHSA-g3vx-3m76-f
• CISA KEV catalog www.cisa.gov/known-exploited-vulnerabilities-catalog
• FIRST EPSS (2026-10-24) api.first.org/data/v1/epss?cve=CVE-2026-110447