Collabora Online Built-in CODE Server: OS command injection in proxy.php
Deadline for US federal agencies: 26 Oct 2026
Summary
The Nextcloud app Collabora Online - Built-in CODE Server (richdocumentscode) contains an OS command injection in proxy.php. An unauthenticated remote attacker can execute commands as the web server user when the built-in CODE server is not running, for example after a restart, upgrade or crash. The vulnerability is actively exploited; attackers have planted web shells and searched for credential and cryptocurrency wallet files. Standalone Collabora Online servers, Docker images and packages are not affected.
Affected
- Nextcloud app Collabora Online - Built-in CODE Server (richdocumentscode) versions before 26.4.303 (v26.4.302 and older)
- Only installations with the built-in CODE server app are affected; standalone Collabora Online, Docker and distribution packages are not affected
Fixed in
- Update the app richdocumentscode to version 26.4.303 or later
Workaround
- No workaround is documented.
- Disabling the app is not sufficient; update it to 26.4.303 or later, or remove it.
- Consider replacing the built-in server with a standalone Collabora Online server, which is not affected.
Exploitation
- Exploited in the wild in September and October 2026.
- Added to the CISA Known Exploited Vulnerabilities catalog on October 23, 2026.
- Attackers placed PHP web shells such as shx*.php and Nx_33143.php under apps/richdocumentscode/ and targeted proxy.php?status.
- Public exploit availability is reported; no exploit details are included here.
- The number of compromised servers is unknown.
Our recommendation
- Update richdocumentscode to 26.4.303 or later, or remove the app if it is not needed.
- Patching alone is not enough if the vulnerable version was exposed: check the app directory for unexpected PHP files and remove them.
- Review web server and access logs for requests to proxy.php, including encoded path traversal and command substitution.
- Rotate credentials that the web server user could read, such as database and application passwords.
- Check whether the Nextcloud version is still supported; Nextcloud 29 and earlier are end of life.
Public exploits
Links to third-party sites, not checked by us – exploit code can contain malware. Only use it in isolated test environments.
- Proof of concept on GitHub (3 repositories)
adriyansyah-mf/cve-2026-110447 · Iceman2050/cve-2026-110447-checker · CyRouteWolf/cve-2026-110447-poc
Research sources
- GitHub Security Advisory GHSA-g3vx-3m76-fghh (Collabora) github.com
- GitHub Advisory GHSA-f97p-r72q-64h2 github.com
- CISA Known Exploited Vulnerabilities Catalog www.cisa.gov
- Nextcloud community: To Collabora Built-in User: Update ASAP help.nextcloud.com
- GitHub issue richdocumentscode #354 github.com
- The Hacker News: Hackers backdoor Nextcloud servers thehackernews.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 30 Oct 2026, 13:34.
Original description (NVD)
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.
Required action (CISA)
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.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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