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Limited Server-Side Request Forgery (SSRF) in Keyword Fetching Functionality

Low
Kovah published GHSA-473x-rmm6-mc8c Nov 3, 2025

Package

No package listed

Affected versions

< v2.3.1

Patched versions

None

Description

Summary

The htmlKeywordsFromUrl function in the FetchController class accepts user-provided URLs and makes HTTP requests to them without validating that the destination is not an internal or private network resource. This Server-Side Request Forgery (SSRF) vulnerability allows authenticated attackers to use the application server to perform port scanning and service discovery on internal networks. However, the practical impact is very limited because the function only extracts content from HTML meta keywords tags, which prevents meaningful data exfiltration from databases, APIs, or cloud metadata endpoints.

Details

The htmlKeywordsFromUrl function in the FetchController class accepts user-provided URLs and makes HTTP requests to them without validating that the destination is not an internal or private network resource. This Server-Side Request Forgery (SSRF) vulnerability allows authenticated attackers to use the application server to perform port scanning and service discovery on internal networks. However, the practical impact is very limited because the function only extracts content from HTML meta keywords tags, which prevents meaningful data exfiltration from databases, APIs, or cloud metadata endpoints.

Vulnerable Endpoints

POST /fetch/keywords-for-url - Accepts user-provided URLs and makes server-side HTTP requests without validation.

The vulnerable code is located in app/Http/Controllers/FetchController.php:

// Lines 95-121
public function htmlKeywordsFromUrl(Request $request)
{
    $request->validate([
        'url' => ['url'], // Only validates URL format, not destination
    ]);

    $url = $request->input('url');
    $newRequest = setupHttpRequest(3);
    $response = $newRequest->get($url); // Makes request to user-provided URL

    if ($response->successful()) {
        $html5 = new HTML5();
        $dom = $html5->loadHTML($response->body());
        $keywords = [];
        foreach ($dom->getElementsByTagName('meta') as $metaTag) {
            if (strtolower($metaTag->getAttribute('name')) === 'keywords') {
                $keywords = explode(',', $metaTag->getAttributeNode('content')?->value);
                $keywords = array_map(fn($keyword) => trim(e($keyword)), $keywords);
                array_push($keywords, ...$keywords);
            }
        }
        return response()->json(['keywords' => $keywords]);
    }

    return response()->json(['keywords' => null]);
}

The function only validates that the input is a properly formatted URL using Laravel's built-in url validation rule, but does not verify the destination IP address. This allows attackers to target localhost (127.0.0.1), private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), link-local addresses (169.254.0.0/16), and other reserved IP ranges. The impact is limited to network reconnaissance as the response parsing only extracts HTML meta keywords, which are not present in database protocols, modern APIs, or cloud metadata endpoints.

PoC

Steps to Reproduce

  1. Log in to LinkAce as any authenticated user
  2. Open the browser developer console
  3. Send a POST request to /fetch/keywords-for-url with a JSON payload containing an external URL: {"url": "https://www.w3schools.com"}. Include the CSRF token from the page metadata
  4. Observe that the server makes the HTTP request and returns keywords from the target page, confirming the SSRF vulnerability
  5. Test internal network access by sending a request with an internal target: {"url": "http://127.0.0.1:80"}
  6. Observe that the server attempts to connect to localhost, demonstrating the ability to probe internal network resources
  7. Repeat with different ports and IP addresses to perform port scanning and service discovery on the internal network
  8. Note that data exfiltration is limited to HTML pages containing meta keywords tags, which excludes most modern services and APIs

Proof of Concept (Media)

PoC Image

Recommendations

Implement IP address validation before making HTTP requests to user-provided URLs. After validating the URL format, extract the hostname using parse_url($url, PHP_URL_HOST), resolve it to an IP address using gethostbyname(), and validate that the IP is not in a private or reserved range using filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE). This will block requests to localhost (127.0.0.1), private networks (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), and link-local addresses (169.254.0.0/16) while still allowing legitimate external URLs. Consider implementing a whitelist of allowed domains if the functionality only needs to support specific external services.

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity High
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity None
Availability Low
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

CVE ID

CVE-2025-62719

Weaknesses

Server-Side Request Forgery (SSRF)

The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. Learn more on MITRE.

Credits