CVE-2021-23358Public exploitNetwork attack vector

Code execution via unsanitized template variable

Published Mar 29, 2021 · Updated Nov 3, 2025

Code injection in Underscore.js 1.3.2 through 1.12.0 and 1.13.0-0 through 1.13.0-1 allows attackers to execute JavaScript. The _.template function passes the unchecked variable option from template settings as an argument name to the Function constructor, allowing injected syntax to enter generated code. Exploitation requires a consuming application to place attacker-controlled data in that option, and successful code runs in the application's JavaScript context.

CVSS severity3.3
Low
EPSS probability4.09%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

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Summary

What happened

Code injection in Underscore.js 1.3.2 through 1.12.0 and 1.13.0-0 through 1.13.0-1 allows attackers to execute JavaScript. The _.template function passes the unchecked variable option from template settings as an argument name to the Function constructor, allowing injected syntax to enter generated code. Exploitation requires a consuming application to place attacker-controlled data in that option, and successful code runs in the application's JavaScript context.

The record

CVE
CVE-2021-23358
Published
Mar 29, 2021
Updated
Nov 3, 2025
Vendor
Jeremy Ashkenas
Product
Underscore.js
Classifications
CWE-94, T1059.007
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Mar 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=1.13.0-0 <unspecified
  2. Affected versionversion=1.3.2 <unspecified
  3. Affected versionversion=unspecified <1.12.1
  4. Affected versionversion=unspecified <1.13.0-2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Jeremy Ashkenas · Underscore.jsversion=1.13.0-0 <unspecified; version=1.3.2 <unspecified; version=unspecified <1.12.1; version=unspecified <1.13.0-2

Published CVSS scores

9.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.3SnykCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:N
3.0SnykCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

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

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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