CVE-2021-40894Public exploitNetwork attack vector

Process hang via deepValueSearch regex backtracking

Published Jun 24, 2022 · Updated Aug 4, 2024

Regular expression denial of service in underscore-99xp 1.7.2 allows remote attackers to hang a Node.js process via a crafted search path. The deepValueSearch function evaluates a regular expression against a caller-supplied property path without constraining pathological input, causing excessive backtracking on a long invalid bracketed segment. The function must receive attacker-controlled input; the public proof of concept uses a long underscore run, and the documented consequence is limited to availability.

CVSS severity7.5
High
EPSS probability1.05%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in underscore-99xp 1.7.2 allows remote attackers to hang a Node.js process via a crafted search path. The deepValueSearch function evaluates a regular expression against a caller-supplied property path without constraining pathological input, causing excessive backtracking on a long invalid bracketed segment. The function must receive attacker-controlled input; the public proof of concept uses a long underscore run, and the documented consequence is limited to availability.

The record

CVE
CVE-2021-40894
Published
Jun 24, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-1333, CAPEC-492, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
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 exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
CAPEC-492Regular Expression Exponential Blowup
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

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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