Can you explain this vulnerability to me?

CVE-2025-15373 is a Server-Side Request Forgery (SSRF) vulnerability in EyouCMS versions up to 1.7.7, specifically in the saveRemote function of application/function.php. The function fetches remote images by making HTTP requests to URLs provided by users but fails to properly validate these URLs. This allows attackers, including authenticated users, to make the server send unauthorized requests to arbitrary internal or external hosts, such as internal network services or cloud metadata endpoints. The vulnerability arises because the function only checks that the URL starts with "http" and that the HTTP response is 200 OK with an image content type, but does not block requests to internal IP ranges or localhost, nor does it prevent DNS rebinding attacks. [1, 2, 3]

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How can this vulnerability impact me? :

This vulnerability can impact you by allowing attackers to leverage the server to access internal network resources that are normally inaccessible from outside, such as databases or cloud metadata services. This can lead to unauthorized disclosure of sensitive information (confidentiality impact), potential manipulation or interference with internal services (integrity impact), and possible denial of service conditions on internal resources (availability impact). Attackers can perform internal network scanning, access sensitive endpoints like 169.254.169.254 for cloud metadata, and probe services running on localhost or private IP ranges. Exploitation requires authentication in some cases but can be performed remotely. [1, 2, 3]

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How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by identifying if your system is running EyouCMS versions up to 1.7.7 and if the vulnerable endpoints are accessible. One detection method is using Google dorking with the query `inurl:application/function.php` to find potentially vulnerable targets. Additionally, monitoring for unusual HTTP requests to internal IP addresses or cloud metadata endpoints from authenticated users can indicate exploitation attempts. Since exploitation requires authentication, reviewing logs for POST requests to endpoints such as `/index.php?m=user&c=Uploadify&a=ueditor&action=catchimage`, `/index.php?m=admin&c=Ueditor&action=catchimage`, and `/index.php?m=admin&c=Uploadimgnew&a=remote` may help detect attacks. Specific commands are not provided, but network monitoring tools and log analysis focusing on these endpoints and suspicious internal requests are recommended. [1, 2]

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What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation steps include applying the vendor's patch by upgrading EyouCMS to version 1.7.8 once it is released. Until then, restrict access to the vulnerable endpoints to trusted users only, especially limiting authenticated user access. Implement network-level controls to block outbound HTTP requests from the server to internal IP ranges (e.g., 127.0.0.1, 10.x.x.x, 172.16.x.x, 192.168.x.x) and cloud metadata IPs (169.254.169.254). Additionally, consider implementing strict URL validation in the application to block requests to internal or private IP addresses, use a whitelist of trusted domains for remote image fetching, disable DNS rebinding attacks by validating resolved IPs before requests, and route outbound requests through a proxy enforcing security policies. [1, 2]

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