CVE-2026-16231: hbs is an Express view engine that wraps Handlebars

Q: How do I fix CVE-2026-16231?

hbs: upgrade to 4.3.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-16231 being exploited?

CVE-2026-16231 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-2026-16231 affect?

CVE-2026-16231 affects hbs. Severity is high (CVSS 8.1). hbs is an Express view engine that wraps Handlebars. Its registerAsyncHelper API bypasses Handlebars' automatic HTML escaping: an async helper returns an opaque placeholder during the first render pass, so the double-brace expression escape

Routine

HIGH 8.1UPGRADE

CVE-2026-16231 is a high-severity flaw (CVSS 8.1) affecting hbs. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

hbs is an Express view engine that wraps Handlebars. Its registerAsyncHelper API bypasses Handlebars' automatic HTML escaping: an async helper returns an opaque placeholder during the first render pass, so the double-brace expression escapes only the placeholder, and after rendering hbs substitutes the placeholder with the raw callback return value without escaping it, across the cached, uncached, and layout render paths. An application that pass

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 66%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-08-25
Last modified	2026-10-06

Publisher (CNA): openjs · Vendor: hbs project

Last updated 2026-10-06 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-25 10:18 UTCPublished CVE record published
2026-10-06 22:10 UTCUpdated Record last modified

hbs project hbs UPGRADE

Affected: >= 2.1.0 and < 4.3.0

Fixed in: 4.3.0

Safe to downgrade to: a release before 2.1.0

1. Check installed version

npm ls hbs

2. UPGRADE to 4.3.0

npm install hbs@">=4.3.0"

3. If no update is available yet, DOWNGRADE to a release before 2.1.0

npm view hbs versions npm install hbs@"<2.1.0"

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-2026-16231?

hbs: upgrade to 4.3.0. Exact commands for each OS are on this page.

Is CVE-2026-16231 being exploited?

CVE-2026-16231 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-2026-16231 affect?

CVE-2026-16231 affects hbs. Severity is high (CVSS 8.1). hbs is an Express view engine that wraps Handlebars. Its registerAsyncHelper API bypasses Handlebars' automatic HTML escaping: an async helper returns an opaque placeholder during the first render pass, so the double-brace expression escape

How urgent is CVE-2026-16231?

Priority 37/100. High severity

References

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