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MEDIUM severity

CVE-2021-3664 — url-parse

MEDIUMFix: unshiftio/url-parse@81ab967

CVE-2021-3664 is a medium-severity (CVSS 5.3) Open Redirect vulnerability in url-parse. 1 public exploit reference exists, so weaponization risk is real. A fix is available for url-parse — see the affected versions and patch details below.

Open redirect in url-parse

Also known asGHSA-hh27-ffr2-f2jc
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.8%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs78th percentile — riskier than 78% of all scored CVEsHighest risk
0.00%0.78%1.56%2.33%0.2%1.8%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-3664 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

3Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream
url-parsenpm
48.9Mdownloads / week

Description

Overview

Affected versions of npm url-parse are vulnerable to URL Redirection to Untrusted Site.

Impact

Depending on library usage and attacker intent, impacts may include allow/block list bypasses, SSRF attacks, open redirects, or other undesired behavior.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmurl-parse≥ 0.1.0&&< 1.5.21.5.2npm install url-parse@1.5.2

Affected Products

1 product · 1 configurations
Application
url-parseurl-parse_project
< 1.5.2
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

url-parse is vulnerable to URL Redirection to Untrusted Site

huntr.devNVDAug 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for url-parse, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update url-parse to 1.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3664 is resolved across your whole dependency graph.

  3. Workarounds

    Stop reflecting attacker-controlled destinations: resolve every redirect target against an allowlist of paths or hosts you own, prefer a server-side key over a full URL in the request, and reject absolute URLs entirely where the flow only ever needs a relative one.

Frequently Asked Questions

# Overview Affected versions of npm `url-parse` are vulnerable to URL Redirection to Untrusted Site. # Impact Depending on library usage and attacker intent, impacts may include allow/block list bypasses, SSRF attacks, open redirects, or other undesired behavior.
O3 Security · Impact-Aware SCA

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CVE-2021-3664: url-parse SSRF — Fixed in 1.5.2