CVE-2021-32821

Regular expression Denial of Service in MooTools

6.2 Medium

MooTools is a collection of JavaScript utilities for JavaScript developers. All known versions include a CSS selector parser that is vulnerable to Regular Expression Denial of Service (ReDoS). An attack requires that an attacker can inject a string into a CSS selector at runtime, which is quite common with e.g. jQuery CSS selectors. No patches are available for this issue.

Attack profile

How easy it is to exploit

Attack vector: Local
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

0.68%Down 0.2 points since Jan 4, 2023

What each source reports

CVE List Score used 6.2

Regular expression Denial of Service in MooTools

Record: CVE-2021-32821
CVSS 3.1: 6.2 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-400
Updated: 2026-11-02

EUVDEUVD-2023-0554 6.2

Record: EUVD-2023-0554
CVSS 3.1: 6.2 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

GitHub AdvisoriesGHSA-v63q-hgqc-qvpg 7.5

MooTools Regular Expression Denial of Service

Record: GHSA-v63q-hgqc-qvpg
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-400, CWE-1333
Updated: 2026-11-02

NVD 6.2

Record: CVE-2021-32821
CVSS 3.1: 6.2 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-400, CWE-1333
Updated: 2026-11-02

OSV 7.5

Record: CVE-2021-32821
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVDEBIAN-CVE-2021-32821 7.5

Record: DEBIAN-CVE-2021-32821
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVGHSA-v63q-hgqc-qvpg 7.5

MooTools Regular Expression Denial of Service

Record: GHSA-v63q-hgqc-qvpg
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-1333, CWE-400
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-32821 6.2

Record: UBUNTU-CVE-2021-32821
CVSS 3.1: 6.2 MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`mootools` npm	through 1.5.2	None known
`mootools` Debian:12	All versions, plus listed versions 1.4.5~debian1-3	None known
`mootools` Debian:13	All versions, plus listed versions 1.4.5~debian1-3	None known
`mootools` Debian:14	All versions, plus listed versions 1.4.5~debian1-3	None known
`mootools` Ubuntu:16.04:LTS	All versions, plus listed versions 1.4.5~debian1-2.1	None known
`mootools` Ubuntu:18.04:LTS	All versions, plus listed versions 1.4.5~debian1-2.1	None known
`mootools` Ubuntu:20.04:LTS	All versions, plus listed versions 1.4.5~debian1-2.1	None known
`mootools` Ubuntu:22.04:LTS	All versions, plus listed versions 1.4.5~debian1-3	None known
`mootools` Ubuntu:24.04:LTS	All versions, plus listed versions 1.4.5~debian1-3	None known
`mootools` Ubuntu:25.10	All versions, plus listed versions 1.4.5~debian1-3	None known
`mootools` Ubuntu:26.10	All versions, plus listed versions 1.4.5~debian1-3build1	None known
`mootools` Ubuntu:26.04:LTS	All versions, plus listed versions 1.4.5~debian1-31.4.5~debian1-3build1	None known

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-32821 is a medium vulnerability (CVSS 6.2) in Mootools, published January 3, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.68%, the 52nd percentile. No source names a fixed version.