How severe is CVE-2021-23369?

CVE-2021-23369 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-23369?

CVE-2021-23369 affects the following packages: org.webjars:handlebars (Maven), org.webjars.npm:handlebars (Maven), org.webjars.bowergithub.wycats:handlebars.js (Maven), handlebars (npm). Ecosystems affected: Maven, npm.

How do I fix CVE-2021-23369?

Update org.webjars:handlebars to 4.7.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23369 is resolved across your whole dependency graph.

How do I detect CVE-2021-23369 in my Maven, npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.webjars:handlebars, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-23369 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2021-23369 actively exploited in the wild?

Yes. There are 4 known exploit references for CVE-2021-23369, including 4 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-23369?

CVE-2021-23369 has an EPSS (Exploit Prediction Scoring System) score of 7.0%, placing it in the 94th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2021-23369 published, and has it been updated?

CVE-2021-23369 was published on April 12, 2021 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven📦 npm

Not in CISA KEV

CRITICAL severity

CVE-2021-23369 — handlebars

CRITICALFix: handlebars-lang/handlebars.js@b6d3de7

CVE-2021-23369 is a critical-severity (CVSS 9.8) remote code execution vulnerability in org.webjars:handlebars. 4 public exploit references exist, so weaponization risk is real. A fix is available for org.webjars:handlebars — see the affected versions and patch details below.

Remote code execution in handlebars when compiling templates

Also known asGHSA-f2jv-r9rf-7988

Published

Apr 12, 2021

Updated

Jul 8, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

4 known

Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

7.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs94th percentile — riskier than 94% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-23369 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

4 pkgs affected

☕org.webjars:handlebars☕org.webjars.npm:handlebars☕org.webjars.bowergithub.wycats:handlebars.js📦handlebars

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

The package handlebars before 4.7.7 are vulnerable to Remote Code Execution (RCE) when selecting certain compiling options to compile templates coming from an untrusted source.

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.webjars:handlebars`	all versions	4.7.7`org.webjars:handlebars:4.7.7`
☕Maven	`org.webjars.npm:handlebars`	all versions	4.7.7`org.webjars.npm:handlebars:4.7.7`
☕Maven	`org.webjars.bowergithub.wycats:handlebars.js`	all versions	4.7.7`org.webjars.bowergithub.wycats:handlebars.js:4.7.7`
📦npm	`handlebars`	all versions	4.7.7`npm install handlebars@4.7.7`

Affected Products

1 product · 1 configurations

Application

handlebarshandlebarsjs

< 4.7.7

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

The package handlebars before 4.7.7 are vulnerable to Remote Code Execut…

snyk.ioNVDJun 2021

The package handlebars before 4.7.7 are vulnerable to Remote Code Execut…

snyk.ioNVDJun 2021

The package handlebars before 4.7.7 are vulnerable to Remote Code Execut…

snyk.ioNVDJun 2021

The package handlebars before 4.7.7 are vulnerable to Remote Code Execut…

snyk.ioNVDJun 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.webjars:handlebars, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.webjars:handlebars to 4.7.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23369 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Red Hat OpenShift Container Platform (OCP) 4 delivers the kibana package which includes Handlebars.js. From OCP 4.6, the kibana package is no longer shipped and will not be fixed. The openshift4/ose-logging-kibana6 container includes Handlebars.js directly as container first code. In OpenShift Container Platform…

Product	Fixed in	Advisory
OpenShift Logging 5.1	`openshift-logging/kibana6-rhel8:v6.8.1-48`	RHSA-2021:4628
OpenShift Logging 5.2	`openshift-logging/kibana6-rhel8:v6.8.1-47`	RHSA-2021:4032
Red Hat OpenShift Container Platform 4.6	`openshift4/ose-logging-kibana6:v4.6.0-202106181629.p0.git.40f3e72`	RHSA-2021:2500
RHPAM 7.13.1 async	`handlebars`	RHSA-2023:1334

Frequently Asked Questions

The package handlebars before 4.7.7 are vulnerable to Remote Code Execution (RCE) when selecting certain compiling options to compile templates coming from an untrusted source.

O3 Security · Impact-Aware SCA

Is CVE-2021-23369 in your dependencies?

Find it across Maven, npm, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

9.8/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

handlebars.js

5.1/10

Code-Review8/10

Maintained3/10

Branch-ProtectionN/A

Assessed Oct 5, 2026

Timeline

Disclosed

Apr 12, 2021

First exploit

Jun 8, 2021

Last updated

Jul 8, 2026

Identifiers

CVE-2021-23369

GHSA-f2jv-r9rf-7988

References

Advisorysecurity.netapp.com Advisorynvd.nist.gov Fixgithub.com Fixgithub.com Websecurity.netapp.com Packagegithub.com Evidencesnyk.io Evidencesnyk.io Evidencesnyk.io Evidencesnyk.io

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedJul 8, 2026

CVE-2021-23369 — handlebars

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Fixing This On Your OS

Frequently Asked Questions

Is CVE-2021-23369 in your dependencies?