CVE-2026-116827 in YesWiki
Summary
by MITRE • 10/27/2026
YesWiki before 4.7.0 contains a server-side request forgery vulnerability in the Bazar CSV import copyUrlToLocalFile() function that allows authenticated administrators to make arbitrary outbound requests by supplying crafted URLs in CSV file or image fields. Attackers can bypass the extension check with a query-string suffix or redirects to fetch cloud metadata credentials, internal services, or local files via file://, with responses stored in the web-accessible files/ directory.
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Analysis
by VulDB Data Team • 10/27/2026
YesWiki versions prior to 4.7.0 are susceptible to a critical server-side request forgery vulnerability located within the Bazar extension's CSV import functionality. Specifically, the copyUrlToLocalFile() function fails to adequately validate or sanitize URLs provided by authenticated administrators during the data ingestion process. This flaw allows an attacker with administrative privileges to craft malicious CSV files containing specially constructed URL fields that trigger arbitrary outbound HTTP requests from the server itself rather than simply importing local file content as intended. The vulnerability stems from a lack of strict allowlisting for destination hosts and protocols, enabling the application to act as a proxy for external entities seeking to probe internal network infrastructure or exfiltrate sensitive data.
The operational impact of this flaw is significant because it leverages existing administrative privileges to bypass standard security boundaries. An attacker can exploit this mechanism by embedding crafted URLs in CSV file paths or image fields during import operations. By utilizing query-string suffixes or exploiting HTTP redirects, the attacker can circumvent basic extension checks that might otherwise restrict access to specific file types. This capability allows for the retrieval of cloud metadata credentials from instance metadata services such as AWS EC2 or Azure Managed Identity endpoints, which are often accessible only within internal network segments and not exposed publicly. Furthermore, the vulnerability permits probing of local internal services running on ports typically inaccessible from external networks, effectively turning the YesWiki server into a pivot point for further lateral movement within the organization's infrastructure.
Beyond network reconnaissance and credential theft, this vulnerability facilitates unauthorized access to sensitive local files through the use of file:// URI schemes. When such URLs are processed, the application stores the fetched content in the web-accessible files/ directory. This behavior not only exposes internal configuration files or source code but also creates a persistent storage mechanism for exfiltrated data that can be subsequently accessed via standard HTTP requests if proper access controls on the upload directory are misconfigured. The combination of outbound request forgery and local file inclusion capabilities significantly expands the attack surface, allowing adversaries to escalate privileges, steal session tokens, or compromise dependent systems within the same trust zone as the vulnerable application.
To mitigate this risk, organizations running YesWiki versions earlier than 4.7.0 should immediately upgrade to the latest patched release where these input validation checks have been strengthened. In cases where immediate upgrading is not feasible, administrators can implement network-level controls such as firewall rules or reverse proxy configurations that restrict outbound connections from the web server to only known and necessary destinations. Additionally, disabling cloud metadata endpoint access at the operating system level using link-local address blocking techniques like 169.254.169.254 can provide a layer of defense against credential theft attempts. It is also advisable to review file upload permissions to ensure that the files/ directory does not allow direct execution or unrestricted reading by unauthenticated users, thereby limiting the impact if data exfiltration occurs.
From a classification perspective, this vulnerability aligns with CWE-918 Server-Side Request Forgery (SSRF), which describes flaws where an application retrieves resources from remote servers using user-supplied URLs without proper validation. The exploitation technique of bypassing extension checks via query strings or redirects also relates to CWE-20 Improper Input Validation, indicating a failure in the sanitization logic before processing. In terms of tactical mapping within the MITRE ATT&CK framework, this vulnerability supports techniques such as T1598 Phishing for Information from Cloud Infrastructure and potentially T1046 Network Service Discovery if used to probe internal services. Addressing these vulnerabilities requires both software patching and robust network segmentation strategies to minimize the blast radius of potential compromises.