Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-3683 is a Server-Side Request Forgery (SSRF) vulnerability found in bufanyun HotGo versions up to 2.0, specifically in the ImageTransferStorage function of the /server/internal/logic/common/upload.go file.'}, {'type': 'paragraph', 'content': 'The vulnerability occurs because the application accepts user-supplied URLs and uses them directly to make HTTP GET requests without properly validating or restricting the destination URLs.'}, {'type': 'paragraph', 'content': 'The function only checks if the URL starts with "http://" or "https://" and then fetches the content, expecting an image response, but it does not block URLs pointing to internal or private network resources.'}, {'type': 'paragraph', 'content': 'This allows authenticated attackers to make the server send requests to internal network services, potentially probing internal services, accessing metadata endpoints, bypassing firewall restrictions, performing port scans, and possibly exfiltrating sensitive data.'}] [1, 2, 3]

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Impact Analysis

This vulnerability can impact you by allowing attackers to exploit the server to send unauthorized requests to internal network resources.

• Probe internal network services to discover sensitive or vulnerable systems.
• Access metadata endpoints that may contain sensitive configuration or credential information.
• Bypass firewall restrictions that normally protect internal services.
• Perform port scanning on internal infrastructure to identify open services.
• Potentially exfiltrate sensitive data from services not intended to be externally accessible.

The exploit is publicly available and easy to use, increasing the risk of compromise.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by monitoring requests to the /admin/upload/imageTransferStorage endpoint, especially those containing URLs pointing to internal or private network resources.'}, {'type': 'paragraph', 'content': 'Since the vulnerability involves server-side requests to user-supplied URLs without proper validation, detection can involve checking server logs for unusual outbound HTTP requests initiated by the application to internal IP addresses or unexpected domains.'}, {'type': 'paragraph', 'content': 'Suggested commands to detect exploitation attempts or suspicious activity include:'}, {'type': 'list_item', 'content': "Using web server access logs to find requests to the vulnerable endpoint, e.g., grep '/admin/upload/imageTransferStorage' /var/log/nginx/access.log"}, {'type': 'list_item', 'content': 'Monitoring outbound HTTP requests from the server to internal IP ranges, e.g., using tcpdump: tcpdump -i eth0 dst net 10.0.0.0/8 or tcpdump -i eth0 dst net 192.168.0.0/16'}, {'type': 'list_item', 'content': 'Checking application logs for errors or stack traces related to internal requests triggered by the ImageTransferStorage function.'}, {'type': 'list_item', 'content': 'Using network scanning tools to detect unusual port scanning or probing activity originating from the server.'}] [1, 3]

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Mitigation Strategies

Immediate mitigation steps include implementing strict validation of URLs accepted by the ImageTransferStorage function to ensure only allowed domains and protocols are used.

Blocking requests to private IP address ranges from the application is critical to prevent SSRF attacks targeting internal services.

Deploying a dedicated egress proxy with filtering capabilities can help control and monitor outbound requests from the application server.

Network segmentation should be applied to isolate the application server from sensitive internal infrastructure.

Conduct thorough security reviews of all functionalities that perform external requests to identify and fix similar issues.

If possible, consider replacing the affected product with an alternative solution, as no vendor patches or countermeasures have been reported.

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