CVE-2026-116826 in YesWiki
Summary
by MITRE • 10/27/2026
YesWiki before 4.7.0 contains a server-side request forgery vulnerability in DuplicationManager::downloadFile() that allows authenticated administrators to make arbitrary outbound requests via the files array. Attackers can POST file:// or internal URLs to /api/pages/{tag}/duplicate, storing local files, cloud metadata, or database credentials in the publicly accessible files/ directory.
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Analysis
by VulDB Data Team • 10/27/2026
The vulnerability identified in YesWiki versions prior to 4.7.0 represents a critical server-side request forgery flaw located within the DuplicationManager::downloadFile() function. This security defect allows authenticated administrators, who possess elevated privileges within the application, to manipulate outbound network requests by injecting malicious payloads into the files array parameter. The core technical failure lies in the insufficient validation of input data provided through this interface, which permits the inclusion of arbitrary Uniform Resource Locators rather than restricting them to expected internal or safe external sources. By exploiting this mechanism via a POST request to the /api/pages/{tag}/duplicate endpoint, an attacker can force the server to fetch resources from unexpected destinations, effectively turning the application into a proxy for unauthorized data exfiltration and local file access.
The operational impact of this vulnerability is severe due to the specific nature of the allowed protocols and storage mechanisms. Attackers are able to utilize file:// URIs or internal URLs to direct the server to read sensitive files from the underlying operating system or internal network services. The fetched content, which may include local configuration files, cloud metadata containing authentication tokens, or database credentials stored in plaintext, is subsequently saved into the publicly accessible files/ directory of the YesWiki installation. This behavior transforms a simple request forgery issue into a significant data exposure risk, as any user with access to the web server can retrieve these sensitive artifacts directly through standard HTTP requests without requiring further authentication for the downloaded content itself.
From an industry standards perspective, this vulnerability aligns closely with CWE-918, which describes Server-Side Request Forgery (SSRF), specifically involving the lack of validation on user-supplied URLs that leads to unauthorized access to internal resources or local files. The exploitation path also intersects with ATT&CK technique T1557, Adversary-in-the-Middle, as the attacker leverages the trusted application server to intercept and relay sensitive information from other systems or local storage locations. Furthermore, the ability to read arbitrary local files corresponds to CWE-200, Exposure of Sensitive Information to an Unauthorized Actor, highlighting the critical failure in access control logic regarding file system operations initiated by web-facing APIs.
Mitigation strategies must prioritize immediate patching and architectural review. The most effective remediation is upgrading YesWiki to version 4.7.0 or later, where this specific input validation flaw has been addressed. In environments where an upgrade is not immediately feasible, administrators should implement strict allow-lists for the URLs permitted in the files array, ensuring that only expected domains and protocols are processed by the DuplicationManager::downloadFile() function. Additionally, restricting file system write permissions to prevent public access to the files/ directory can mitigate the impact of data exfiltration, although this is a compensating control rather than a root cause fix. Regular security audits of API endpoints that handle user-supplied URLs are essential to detect similar SSRF patterns in other modules before they can be exploited by malicious actors seeking to compromise system integrity and confidentiality.