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.

What CVEs are caused by CWE-918?

2,178 recorded CVEs are attributed to CWE-918, including CVE-2026-15409, CVE-2021-34473, CVE-2021-21985. 20 are listed in CISA's Known Exploited Vulnerabilities (KEV) catalog.

How is CWE-918 detected?

Automated Static Analysis: Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

What are the consequences of CWE-918?

Exploiting CWE-918 can lead to: Read Application Data, Execute Unauthorized Code or Commands, Bypass Protection Mechanism.

Is CWE-918 actively exploited?

Yes. 20 CWE-918 vulnerabilities are in CISA's KEV catalog of actively exploited flaws, out of 2,178 recorded CVEs.

CWE-918: Server-Side Request Forgery (SSRF) (XSPA)

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Code examples

Illustrative examples from MITRE showing how the weakness appears in code.

This code intends to receive a URL from a user, access the URL, and return the results to the user.

Vulnerable example

php

$url = $_GET['url'];

The given PHP code is vulnerable to Server-Side Request Forgery (SSRF) because it directly accepts a user-supplied URL from the $_GET['url'] parameter and fetches its content using file_get_contents(), without any validation or restrictions. This allows an attacker to request internal or restricted resources within the server's network, such as internal admin panels, cloud metadata endpoints, or local services running on localhost.

CWE-918: Server-Side Request Forgery (SSRF)

Overview

Real-world CVEs

Common consequences

How it happens

When it is introduced

Applies to

How to detect it

Automated Static Analysis

Code examples

Illustrative examples

Terminology & mappings

Alternate terms

Attack patterns

Frequently asked questions

References

Stay ahead of CWE-918

Overview

Real-world CVEs

Common consequences

How it happens

When it is introduced

Applies to

How to detect it

Automated Static Analysis

Code examples

Illustrative examples

Related weaknesses

Parent

Terminology & mappings

Alternate terms

Attack patterns

Frequently asked questions

References

Stay ahead of CWE-918