How severe is CVE-2020-28501?

CVE-2020-28501 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2020-28501?

CVE-2020-28501 affects the following packages: es6-crawler-detect (npm). Ecosystems affected: npm.

How do I fix CVE-2020-28501?

Update es6-crawler-detect to 3.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-28501 is resolved across your whole dependency graph.

How do I detect CVE-2020-28501 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for es6-crawler-detect, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2020-28501 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2020-28501 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2020-28501, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2020-28501?

CVE-2020-28501 has an EPSS (Exploit Prediction Scoring System) score of 1.5%, placing it in the 73th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2020-28501 published, and has it been updated?

CVE-2020-28501 was published on April 13, 2021 and was last updated on March 13, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

CVE-2020-28501 — es6-crawler-detect

MEDIUMFix: JefferyHus/es6-crawler-detect#27

CVE-2020-28501 is a medium-severity (CVSS 5.3) vulnerability in es6-crawler-detect. 1 public exploit reference exists, so weaponization risk is real. A fix is available for es6-crawler-detect — see the affected versions and patch details below.

Regular Expression Denial of Service (ReDoS) in es6-crawler-detect

Published

Apr 13, 2021

Updated

Mar 13, 2026

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 ↗

1.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs73th percentile — riskier than 73% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2020-28501 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.

8other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

es6-crawler-detectnpm

7Kdownloads / week

Description

This affects the package es6-crawler-detect before 3.1.3. No limitation of user agent string length supplied to regex operators.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`es6-crawler-detect`	all versions	3.1.3`npm install es6-crawler-detect@3.1.3`

Affected Products

1 product · 1 configurations

Application

crawlerdetectcrawlerdetect_project

< 3.1.3

range

Exploits & PoCs

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

This affects the package es6-crawler-detect before 3.1.3. No limitation …

snyk.ioNVDMar 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for es6-crawler-detect, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update es6-crawler-detect to 3.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-28501 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

This affects the package es6-crawler-detect before 3.1.3. No limitation of user agent string length supplied to regex operators.

O3 Security · Impact-Aware SCA

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