CVE-2026-84282 in ONLYOFFICE ownCloud Integration Plugin
Summary
by MITRE • 09/08/2026
A Server-Side Request Forgery (SSRF) vulnerability exists in the ONLYOFFICE ownCloud Integration plugin version 9.12. The /apps/onlyoffice/ajax/settings/address endpoint does not sufficiently validate the user-supplied Document Server URL before initiating outbound connections. An authenticated administrator can manipulate the document server parameter to cause the ownCloud server to send arbitrary requests to attacker-controlled destinations, including localhost and internal network hosts. This allows internal network reconnaissance and TCP port scanning based on differences in server responses.
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Analysis
by VulDB Data Team • 09/08/2026
The vulnerability identified as a Server-Side Request Forgery (SSRF) within the ONLYOFFICE integration plugin for ownCloud version 9.12 represents a critical failure in input validation mechanisms governing outbound HTTP requests. This flaw is located specifically at the /apps/onlyoffice/ajax/settings/address endpoint, which serves as the configuration interface where administrators define the URL of the associated Document Server. The core technical deficiency lies in the application's inability to sufficiently sanitize or validate user-supplied values before initiating network connections. By accepting arbitrary URLs without rigorous checks against a whitelist of allowed domains or protocols, the system inadvertently allows an attacker to dictate the destination and nature of server-side requests. This architectural oversight transforms a standard administrative configuration tool into a vector for internal network exploitation, bypassing traditional perimeter defenses that typically monitor external traffic but may not inspect outbound connections initiated by trusted application processes.
The operational impact of this vulnerability is severe due to the authentication requirement being limited to an administrator role. While SSRF vulnerabilities are often mitigated by requiring high-privilege access, in many enterprise environments, administrative credentials can be compromised through phishing, credential stuffing, or other lateral movement techniques once initial foothold is established. Once authenticated as an administrator, a malicious actor can manipulate the document server parameter to force the ownCloud server to send requests to arbitrary destinations controlled by the attacker. This capability extends beyond simple external probing; it allows for extensive internal network reconnaissance and TCP port scanning. By analyzing differences in server responses such as time delays, connection resets, or HTTP status codes, an attacker can map out the internal network topology, identify active services on localhost or other private IP addresses, and potentially discover sensitive backend systems that are not exposed to the public internet.
From a classification perspective, this vulnerability aligns with CWE-918, which defines Server-Side Request Forgery as a flaw where a web server retrieves a specified resource from a user-supplied URL without validating it properly. The exploitation technique leverages ATT&CK tactic T1046, Network Service Discovery, specifically the sub-technique of Port Scanning via SSRF. This method allows attackers to enumerate open ports and running services on internal hosts by observing how the vulnerable server reacts to different connection attempts. Because the requests originate from the ownCloud server itself, they often bypass firewall rules that trust traffic originating from known application servers, making detection significantly more difficult for security monitoring tools that do not perform deep packet inspection or behavioral analysis of outbound connections.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The most effective solution is to upgrade the ONLYOFFICE integration plugin to a version where this validation flaw has been patched by the vendor, ensuring that only pre-approved Document Server URLs are accepted. In environments where upgrading is not immediately feasible, network-level controls should be implemented to restrict outbound HTTP traffic from the ownCloud server to known internal and external endpoints. Additionally, implementing strict input validation on the application side to enforce a whitelist of allowed domains and protocols for the document server parameter is essential. Security teams should also monitor outbound connection logs for anomalies, such as requests directed toward private IP ranges or unusual ports, which may indicate active exploitation attempts. Regular audits of administrative account activity can further reduce the risk associated with compromised credentials being used to trigger this SSRF condition.