Summary
A server-side request forgery vulnerability in decolua 9Router can cause the Search Endpoint to request attacker-controlled destinations through the provider_options.baseUrl value.
When the endpoint accepts a remotely influenced base URL without sufficient validation, an attacker may access internal services or other network resources reachable from the server.
Affected context
This issue affects 9Router deployments through the Search Endpoint and its use of the fetch function in src/shared/utils/ssrfGuard.js. The risk is present where provider_options.baseUrl can be influenced by an external requester and the application permits requests to destinations that should not be reachable through the server.
Exploit preconditions
- Attack surface: The remotely accessible Search Endpoint
- Required access: Ability to submit or influence request parameters containing
provider_options.baseUrl - Trigger point: Server-side fetching performed by the Search Endpoint
- Why exploitation is possible: Insufficient destination validation may allow the server to issue requests to attacker-selected or otherwise restricted network locations
Why this happens
The vulnerability results from treating a caller-influenced URL as a permissible server-side request destination without sufficiently enforcing trust boundaries.
This behavior maps to CWE-918: Server-Side Request Forgery, where an application makes network requests based on attacker-controlled input. Insecure URL validation, incomplete filtering, or reliance on client-side restrictions can allow requests to internal, local, or otherwise unintended services.
Potential impact
- An attacker may retrieve responses from internal services
- The application could expose metadata or other network-accessible information
- The server may be used to reach administrative or otherwise restricted endpoints
- Internal services could receive unintended requests originating from the application
- Network segmentation assumptions may be weakened
General mitigation guidance
Mitigation generally focuses on reducing input control over outbound destinations and enforcing a narrowly defined request policy.
Common defensive patterns include:
- Prefer fixed, allowlisted provider destinations over caller-supplied URLs
- Parse and validate URLs using a centralized policy that restricts schemes, hosts, ports, and redirect targets
- Resolve hostnames and prevent access to loopback, link-local, private, and other restricted address ranges
- Revalidate destinations after redirects and account for DNS resolution changes
- Route outbound requests through controlled egress proxies or network policies
- Apply least-privilege network permissions to the service
- Avoid returning unrestricted upstream responses to callers
How teams detect issues like this
Organizations can look for SSRF risks through:
- Static analysis rules identifying network clients that consume request-derived URLs
- Code review checks for URL validation, redirect handling, DNS rebinding, and private-address filtering
- Runtime logging of outbound destinations, resolved addresses, redirects, and unusual request patterns
- Egress policies that alert on or block connections to internal and metadata address ranges
- Security tests that verify allowlists and reject restricted schemes, hosts, ports, and address ranges
- Automated application security review tools that flag attacker-controlled inputs reaching outbound request functions
