Regular Expression Denial of Service (ReDoS)

published 2021-03-22 5 y ago modified 2026-06-17 4 mo ago also GHSA-jxg6-fhwc-9v9c , EUVD-2021-0844

cvss: 5.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.5%; EPSS 1.5% chance of exploitation in 30 days, percentile 74%
public exploits: 0; none known

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

Patch / fix

fixed in 2 links 1

npm es6-crawler-detect 3.1.3
n/a es6-crawler-detect 3.1.3

github.com/JefferyHus/es6-crawler-detect#27 pull request

Exploit prediction

1.50% chance of exploitation in the next 30 days, higher than 74% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

snyk.io https://snyk.io/vuln/SNYK-JS-ES6CRAWLERDETECT-1051529 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem	package	affected	fixed in
npm	es6-crawler-detect	<3.1.3	3.1.3

Affected products

n/a es6-crawler-detect

Classification

Weakness

CWE-400 Uncontrolled Resource Consumption

References

github.com /JefferyHus/es6-crawler-detect/pull/27
web, patch, third-party-advisory
snyk.io /vuln/SNYK-JS-ES6CRAWLERDETECT-1051529
web, exploit, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2020-28501
advisory

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary