CVE-2021-23364: The package browserslist from 4.0.0 and before 4.16.5 are vulnerable to Regular Expression Denial of Service (

Q: How do I fix CVE-2021-23364?

browserslist: upgrade to 4.16.5. Exact commands for each OS are on this page.

Q: Is CVE-2021-23364 being exploited?

CVE-2021-23364 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-23364 affect?

CVE-2021-23364 affects browserslist. Severity is medium (CVSS 5.3). The package browserslist from 4.0.0 and before 4.16.5 are vulnerable to Regular Expression Denial of Service (ReDoS) during parsing of queries.

Q: How urgent is CVE-2021-23364?

Priority 50/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.3REMOTEUPGRADE

CVE-2021-23364 is a medium-severity flaw (CVSS 5.3) affecting browserslist. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The package browserslist from 4.0.0 and before 4.16.5 are vulnerable to Regular Expression Denial of Service (ReDoS) during parsing of queries.

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.4% (top 16%)
CISA exploited list	No
Weakness	CWE-1333
Published	2021-04-28
Last modified	2026-06-17

Publisher (CNA): Snyk · Vendor: browserslist project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-04-28 16:15 UTCPublished CVE record published
2026-06-17 03:38 UTCUpdated Record last modified

browserslist project browserslist UPGRADE

Affected: >= 4.0.0 and < 4.16.5

Fixed in: 4.16.5

Safe to downgrade to: a release before 4.0.0

1. Check installed version

npm ls browserslist

2. UPGRADE to 4.16.5

npm install browserslist@">=4.16.5"

3. If no update is available yet, DOWNGRADE to a release before 4.0.0

npm view browserslist versions npm install browserslist@"<4.0.0"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-23364?

browserslist: upgrade to 4.16.5. Exact commands for each OS are on this page.

Is CVE-2021-23364 being exploited?

CVE-2021-23364 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-23364 affect?

CVE-2021-23364 affects browserslist. Severity is medium (CVSS 5.3). The package browserslist from 4.0.0 and before 4.16.5 are vulnerable to Regular Expression Denial of Service (ReDoS) during parsing of queries.

How urgent is CVE-2021-23364?

Priority 50/100. Public exploit reference; Remotely exploitable, no login, no user action

References

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