CVE-2021-43306Public exploitNetwork attack vector

Service interruption via exponential URL regex backtracking

Published Jun 1, 2022 · Updated Sep 16, 2024

Regular expression denial of service in jQuery Validation Plugin before 1.19.4 allows remote attackers to interrupt client-side validation. The url2 method applies an inefficient URL-matching regular expression to arbitrary form input, causing exponential backtracking that blocks JavaScript execution. Exposure requires an application to load the additional-methods module and invoke url2 on attacker-controlled input; the resulting service interrupt is confined to the browser execution context.

CVSS severity7.5
High
EPSS probability1.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Regular expression denial of service in jQuery Validation Plugin before 1.19.4 allows remote attackers to interrupt client-side validation. The url2 method applies an inefficient URL-matching regular expression to arbitrary form input, causing exponential backtracking that blocks JavaScript execution. Exposure requires an application to load the additional-methods module and invoke url2 on attacker-controlled input; the resulting service interrupt is confined to the browser execution context.

The record

CVE
CVE-2021-43306
Published
Jun 1, 2022
Updated
Sep 16, 2024
Vendor
jQuery Validation
Product
jQuery Validation Plugin
Classifications
CWE-1333, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 1, 2022CVE 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=unspecified <1.19.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

jQuery Validation · jQuery Validation Pluginversion=unspecified <1.19.4

Published CVSS scores

5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.9JFrogCVSS:3.1/AV:N/AC:H/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
T1499Endpoint Denial of Service

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo