CVE-2025-66208 in Online
Summary
by MITRE • 12/03/2025
Collabora Online - Built-in CODE Server (richdocumentscode) provides a built-in server with all of the document editing features of Collabora Online. In versions prior to 25.04.702, Collabora Online has a Configuration-Dependent RCE (OS Command Injection) in richdocumentscode proxy. Users of Nextcloud with Collabora Online - Built-in CODE Server app can be vulnerable to attack via proxy.php and an intermediate reverse proxy. This vulnerability is fixed in 25.04.702.
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Analysis
by VulDB Data Team • 12/08/2025
The vulnerability CVE-2025-66208 represents a critical configuration-dependent remote code execution flaw in Collabora Online's built-in CODE Server component known as richdocumentscode. This vulnerability specifically affects versions prior to 25.04.702 and resides within the proxy functionality that handles document editing operations. The flaw manifests as an operating system command injection vulnerability that can be exploited through the proxy.php endpoint when Collabora Online operates behind an intermediate reverse proxy configuration. The security implications are severe as this vulnerability allows attackers to execute arbitrary commands on the affected system with the privileges of the web server process. The issue stems from insufficient input validation and sanitization within the proxy handling logic, creating a pathway for malicious actors to inject and execute OS commands through crafted requests that traverse the proxy infrastructure.
The technical exploitation of this vulnerability requires a specific configuration scenario involving Nextcloud deployments where Collabora Online's built-in CODE Server is utilized alongside an intermediate reverse proxy. Attackers can leverage this weakness by crafting malicious requests that exploit the command injection vulnerability in the proxy.php file, which then gets processed by the richdocumentscode component. The vulnerability is classified as a configuration-dependent issue because it only manifests when specific deployment patterns are present, particularly those involving reverse proxy configurations that forward requests to the Collabora Online server. This characteristic makes the vulnerability more challenging to detect during routine security assessments since it requires verification of the specific deployment architecture. The flaw directly maps to CWE-77 in the Common Weakness Enumeration catalog, which specifically addresses command injection vulnerabilities that occur when operating system commands are constructed using untrusted input without proper sanitization.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with complete control over the affected Collabora Online server and potentially the entire underlying infrastructure. Organizations using Nextcloud with Collabora Online are at risk of data breaches, system compromise, and unauthorized access to sensitive documents stored within the platform. The vulnerability affects collaborative document editing environments where multiple users interact with shared documents, making it particularly dangerous in enterprise settings where sensitive business information is regularly processed. Attackers can leverage this vulnerability to establish persistent access, exfiltrate confidential data, or deploy additional malicious payloads within the compromised environment. The presence of an intermediate reverse proxy in the deployment architecture creates an additional attack vector that can be exploited through the proxy chain, potentially allowing attackers to bypass certain network security controls that might otherwise protect the internal Collabora Online server.
Mitigation strategies for CVE-2025-66208 require immediate action to upgrade to version 25.04.702 or later, which contains the necessary security patches to address the command injection vulnerability. Organizations should implement network segmentation and access controls to limit exposure of the proxy.php endpoint and related components to untrusted networks. Security monitoring should be enhanced to detect anomalous command execution patterns or unusual proxy behavior that might indicate exploitation attempts. The fix addresses the vulnerability by implementing proper input validation and sanitization measures within the proxy handling code, ensuring that user-supplied data cannot be interpreted as executable commands. Additionally, organizations should conduct thorough security assessments of their Nextcloud deployments to identify any other potential configuration issues that might create similar vulnerabilities. The remediation process should include verification that the reverse proxy configuration properly handles requests without exposing the underlying Collabora Online server to command injection attacks. This vulnerability serves as a reminder of the importance of maintaining current security patches and implementing proper security controls in collaborative document environments where multiple users interact with shared resources. The ATT&CK framework categorizes this vulnerability under T1059.001 for command and scripting interpreter, indicating the exploitation technique used to achieve remote code execution through operating system command injection.