CVE-2026-33939Public exploitNetwork attack vector

Process crash via unchecked decorator invocation

Published Mar 27, 2026 · Updated Mar 27, 2026

Denial of service in Handlebars.js 4.0.0 through 4.7.8 allows remote attackers to crash Node.js processes via unregistered decorators. Generated decorator code in lib/handlebars/compiler/javascript-compiler.js calls the lookupProperty result as a function without checking whether the decorator exists. Exposure requires an application to compile and render attacker-supplied templates without catching the resulting exception, and one crafted request terminates the process.

CVSS severity7.5
High
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Handlebars.js 4.0.0 through 4.7.8 allows remote attackers to crash Node.js processes via unregistered decorators. Generated decorator code in lib/handlebars/compiler/javascript-compiler.js calls the lookupProperty result as a function without checking whether the decorator exists. Exposure requires an application to compile and render attacker-supplied templates without catching the resulting exception, and one crafted request terminates the process.

The record

CVE
CVE-2026-33939
Published
Mar 27, 2026
Updated
Mar 27, 2026
Vendor
Handlebars
Product
Handlebars.js
Classifications
CWE-754, CWE-248, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.0.0, < 4.7.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Handlebars · Handlebars.jsversion=>= 4.0.0, < 4.7.9

Published CVSS scores

7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
CWE-248Uncaught Exception
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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