CVE-2023-24540Network attack vector

Cross-site scripting via incomplete JavaScript whitespace recognition

Published May 11, 2023 · Updated Jan 24, 2025

Cross-site scripting in Go standard library html/template before 1.19.9 and 1.20.0 through 1.20.3 allows attackers to inject JavaScript. The nextJSCtx context tracker recognizes an incomplete whitespace set, so other valid JavaScript whitespace can preserve the wrong token context and cause Template.Execute or ExecuteTemplate to apply inadequate escaping to an action. Exploitation requires a trusted template with an action in the affected JavaScript context and attacker-controlled action data; injected script runs when the generated HTML is rendered.

CVSS severity9.8
Critical
EPSS probability1.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Go standard library html/template before 1.19.9 and 1.20.0 through 1.20.3 allows attackers to inject JavaScript. The nextJSCtx context tracker recognizes an incomplete whitespace set, so other valid JavaScript whitespace can preserve the wrong token context and cause Template.Execute or ExecuteTemplate to apply inadequate escaping to an action. Exploitation requires a trusted template with an action in the affected JavaScript context and attacker-controlled action data; injected script runs when the generated HTML is rendered.

The record

CVE
CVE-2023-24540
Published
May 11, 2023
Updated
Jan 24, 2025
Vendor
Go standard library
Product
html/template
Classifications
CWE-74, CWE-77, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 11, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 24, 2025Record 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=0 <1.19.9
  2. Affected versionversion=1.20.0-0 <1.20.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Go standard library · html/templateversion=0 <1.19.9; version=1.20.0-0 <1.20.4

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CWE-77Improper Neutralization of Special Elements used in a Command ('Command 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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