Summary
A server-side request forgery vulnerability in EyouCMS affects the remote_file_to_local function and allows a remote attacker to influence requests made by the server.
If attacker-controlled or insufficiently validated destinations are accepted, the server may be induced to access internal services or restricted network resources.
A server-side request forgery vulnerability in EyouCMS affects the remote_file_to_local function and allows a remote attacker to influence requests made by the server.
If attacker-controlled or insufficiently validated destinations are accepted, the server may be induced to access internal services or restricted network resources.
Affected context
This issue occurs in EyouCMS deployments using the remote_file_to_local function in application/function.php. Risk increases when remote users can provide or influence a file or URL location and the application does not sufficiently restrict outbound requests, validate destination schemes, or limit access to internal network ranges.
This issue occurs in EyouCMS deployments using the remote_file_to_local function in application/function.php. Risk increases when remote users can provide or influence a file or URL location and the application does not sufficiently restrict outbound requests, validate destination schemes, or limit access to internal network ranges.
Exploit preconditions
- Attack surface: A remotely reachable EyouCMS feature that invokes
remote_file_to_local - Required access: The ability to submit or influence a remote file location; authentication requirements depend on the calling endpoint
- Trigger point: Processing of the attacker-influenced remote resource request
- Why exploitation is possible: The server may make outbound requests without adequately constraining the destination, allowing requests to reach resources unavailable to the external attacker
- Attack surface: A remotely reachable EyouCMS feature that invokes
remote_file_to_local - Required access: The ability to submit or influence a remote file location; authentication requirements depend on the calling endpoint
- Trigger point: Processing of the attacker-influenced remote resource request
- Why exploitation is possible: The server may make outbound requests without adequately constraining the destination, allowing requests to reach resources unavailable to the external attacker
Why this happens
The underlying bug is insufficient validation and destination control for server-initiated network requests.
When application logic retrieves a remote file based on user-influenced input without enforcing trusted schemes, allowed hosts, resolved addresses, and network boundaries, the server becomes an unintended proxy. This maps to CWE-918: Server-Side Request Forgery, in which untrusted input controls requests originating from the vulnerable server.
The underlying bug is insufficient validation and destination control for server-initiated network requests.
When application logic retrieves a remote file based on user-influenced input without enforcing trusted schemes, allowed hosts, resolved addresses, and network boundaries, the server becomes an unintended proxy. This maps to CWE-918: Server-Side Request Forgery, in which untrusted input controls requests originating from the vulnerable server.
Potential impact
- An attacker may access internal services that are not exposed publicly
- Sensitive response data could be disclosed through the application
- Cloud or infrastructure metadata may be reachable where network controls permit it
- Internal administrative interfaces could be probed or abused
- The server could be used to send requests to protected network resources
- An attacker may access internal services that are not exposed publicly
- Sensitive response data could be disclosed through the application
- Cloud or infrastructure metadata may be reachable where network controls permit it
- Internal administrative interfaces could be probed or abused
- The server could be used to send requests to protected network resources
General mitigation guidance
Mitigation generally focuses on reducing trust in user-supplied destinations and enforcing outbound network policy.
Common defensive patterns include:
- Allowing only explicitly approved schemes, hosts, ports, and resource locations
- Resolving hostnames and validating resulting addresses against private, loopback, link-local, and reserved ranges
- Rechecking destinations after redirects and preventing unsafe redirect chains
- Applying egress firewall rules and network segmentation
- Using dedicated retrieval services with minimal privileges and constrained connectivity
- Avoiding direct retrieval of arbitrary URLs when a controlled identifier or approved repository can be used instead
Mitigation generally focuses on reducing trust in user-supplied destinations and enforcing outbound network policy.
Common defensive patterns include:
- Allowing only explicitly approved schemes, hosts, ports, and resource locations
- Resolving hostnames and validating resulting addresses against private, loopback, link-local, and reserved ranges
- Rechecking destinations after redirects and preventing unsafe redirect chains
- Applying egress firewall rules and network segmentation
- Using dedicated retrieval services with minimal privileges and constrained connectivity
- Avoiding direct retrieval of arbitrary URLs when a controlled identifier or approved repository can be used instead
How teams detect issues like this
Organizations commonly detect SSRF risks through:
- Static analysis for HTTP clients, URL fetchers, and file-download functions receiving request-derived input
- Code review checks for missing scheme, hostname, port, redirect, and private-address validation
- Tests that exercise loopback, link-local, private, reserved, and encoded destination forms
- Egress monitoring for unexpected requests from application processes to internal services
- Network policy enforcement that restricts application containers or servers from reaching sensitive ranges
Automated security review tools can help identify request flows from external input to outbound network operations.
Organizations commonly detect SSRF risks through:
- Static analysis for HTTP clients, URL fetchers, and file-download functions receiving request-derived input
- Code review checks for missing scheme, hostname, port, redirect, and private-address validation
- Tests that exercise loopback, link-local, private, reserved, and encoded destination forms
- Egress monitoring for unexpected requests from application processes to internal services
- Network policy enforcement that restricts application containers or servers from reaching sensitive ranges
Automated security review tools can help identify request flows from external input to outbound network operations.
