CVE-2026-33939: Handlebars provides the power necessary to let users build semantic templates

Q: How do I fix CVE-2026-33939?

handlebars: upgrade to 4.7.9. Exact commands for each OS are on this page.

Q: Is CVE-2026-33939 being exploited?

CVE-2026-33939 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-2026-33939 affect?

CVE-2026-33939 affects handlebars. Severity is high (CVSS 7.5). Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled templat

Q: How urgent is CVE-2026-33939?

Priority 49/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-33939 is a high-severity flaw (CVSS 7.5) affecting handlebars. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled template calls `lookupProperty(decorators, "n")`, which returns `undefined`. The runtime then immediately invokes the result as a function, causing an unhandled `TypeError: ... is not a function` that crashes the Node

Why this priority

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

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 50%)
CISA exploited list	No
Weakness	CWE-754, CWE-248
Published	2026-03-27
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: handlebarsjs

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-27 22:16 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

handlebarsjs handlebars UPGRADE

Affected: >= 4.0.0 and < 4.7.9

Fixed in: 4.7.9

Safe to downgrade to: a release before 4.0.0

1. Check installed version

npm ls handlebars

2. UPGRADE to 4.7.9

npm install handlebars@">=4.7.9"

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

npm view handlebars versions npm install handlebars@"<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-2026-33939?

handlebars: upgrade to 4.7.9. Exact commands for each OS are on this page.

Is CVE-2026-33939 being exploited?

CVE-2026-33939 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-2026-33939 affect?

CVE-2026-33939 affects handlebars. Severity is high (CVSS 7.5). Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled templat

How urgent is CVE-2026-33939?

Priority 49/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-33937 CRITICAL 9.8 UPGRADE Handlebars provides the power necessary to let users build semantic templates
CVE-2026-33938 HIGH 8.1 UPGRADE Handlebars provides the power necessary to let users build semantic templates
CVE-2026-33940 HIGH 8.1 UPGRADE Handlebars provides the power necessary to let users build semantic templates
CVE-2026-33941 HIGH 8.2 UPGRADE Handlebars provides the power necessary to let users build semantic templates
CVE-2026-33916 MEDIUM 4.7 UPGRADE Handlebars provides the power necessary to let users build semantic templates

References

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