CVE-2020-28501Network attack vector

Service interruption via unbounded user-agent regex evaluation

Published Mar 22, 2021 · Updated Sep 16, 2024

ReDoS in JefferyHus es6-crawler-detect before 3.1.3 allows remote attackers to interrupt service via crafted user-agent strings. The user-agent scanning path passes an unrestricted string to regular-expression matchers, allowing excessive CPU consumption during evaluation. Exploitation requires a consuming application to process attacker-controlled request headers; the documented consequence is degraded availability without data disclosure or modification.

CVSS severity5.3
Medium
EPSS probability1.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

ReDoS in JefferyHus es6-crawler-detect before 3.1.3 allows remote attackers to interrupt service via crafted user-agent strings. The user-agent scanning path passes an unrestricted string to regular-expression matchers, allowing excessive CPU consumption during evaluation. Exploitation requires a consuming application to process attacker-controlled request headers; the documented consequence is degraded availability without data disclosure or modification.

The record

CVE
CVE-2020-28501
Published
Mar 22, 2021
Updated
Sep 16, 2024
Vendor
JefferyHus
Product
es6-crawler-detect
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <3.1.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

JefferyHus · es6-crawler-detectversion=unspecified <3.1.3

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
5.3SnykCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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