CWE-918 SSRF

Coverage: 25 rules in the SiteShadow rule registry target this CWE (registry v2.0.0). Regex 21Other-pattern 4 Also: Taint and heuristic analyzers may also detect related flows (see coverage for the authoritative list) Registry tagging shows intent, for sample-level behaviour and benchmarked gaps see known gaps.

What this means

SiteShadow flagged code where the server makes outbound requests to a destination influenced by untrusted input (URL parameters, request body, headers, webhook data).

Why it matters

SSRF can expose internal services or cloud metadata.

• Cloud credential theft: SSRF can hit metadata endpoints and steal IAM tokens.
• Internal network access: attackers can reach internal services not exposed publicly.
• Pivoting: SSRF can chain into RCE/data theft via internal admin panels.

Safer examples

1) Allowlist destinations (recommended)

const allowedHosts = new Set(["api.stripe.com", "webhook.partner.com"]);
const u = new URL(req.body.url);
if (!allowedHosts.has(u.host)) throw new Error("Destination not allowed");

2) Block private/metadata ranges and handle redirects safely

Block localhost, RFC1918, link-local, and cloud metadata; limit redirects and prevent DNS rebinding where feasible.

3) Apply tight outbound controls

• Short timeouts
• Limit schemes to https
• Restrict ports to expected values

How SiteShadow detects it (high level)

• Detects outbound HTTP client usage and tracks whether the destination is derived from untrusted input.
• Flags missing allowlists/validation, especially when redirects are enabled.

References

• CWE-918: https://cwe.mitre.org/data/definitions/918.html

---

← Back to Vulnerability Library