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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

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.

How does O3 Security protect against CVE-2020-28501?

O3 pinpoints whether CVE-2020-28501 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

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.

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

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. O3 Security confirms whether CVE-2020-28501 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

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 Mar 13, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

📦es6-crawler-detect

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.

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

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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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.
How O3 protects you
O3 pinpoints whether CVE-2020-28501 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2020-28501. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

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

Is CVE-2020-28501 in your dependencies?

O3 detects CVE-2020-28501 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works