CVE-2021-23369Network attack vector

Code execution via unescaped compat-mode path names

Published Apr 12, 2021 · Updated Sep 16, 2024

Code injection in Handlebars.js before 4.7.7 allows remote attackers to execute code by compiling untrusted templates in compat mode. JavaScriptCompiler.depthedLookup concatenates an attacker-controlled path name into generated JavaScript without JSON string escaping. Exploitation requires an application to compile attacker-controlled templates with the nondefault compat option and then evaluate the generated function.

CVSS severity9.8
Critical
EPSS probability7.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in Handlebars.js before 4.7.7 allows remote attackers to execute code by compiling untrusted templates in compat mode. JavaScriptCompiler.depthedLookup concatenates an attacker-controlled path name into generated JavaScript without JSON string escaping. Exploitation requires an application to compile attacker-controlled templates with the nondefault compat option and then evaluate the generated function.

The record

CVE
CVE-2021-23369
Published
Apr 12, 2021
Updated
Sep 16, 2024
Vendor
Handlebars
Product
Handlebars.js
Classifications
CWE-94, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record 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=unspecified <4.7.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Handlebars · Handlebars.jsversion=unspecified <4.7.7

Published CVSS scores

5.6Snyk CNACVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
5.1Snyk CNACVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1059.007JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

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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