CVE-2023-29400Network attack vector

HTML attribute injection via empty unquoted values

Published May 11, 2023 · Updated Jan 24, 2025

Attribute injection in Go standard library html/template before 1.19.9 and 1.20.0 through 1.20.3 allows attackers to add HTML attributes. htmlNospaceEscaper returns an empty string for an empty action in an unquoted attribute, letting HTML normalization reinterpret following text as attributes. Reachability requires an application to execute such a template with empty input; injected attributes can alter rendered tag behavior.

CVSS severity7.3
High
EPSS probability1.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Attribute injection in Go standard library html/template before 1.19.9 and 1.20.0 through 1.20.3 allows attackers to add HTML attributes. htmlNospaceEscaper returns an empty string for an empty action in an unquoted attribute, letting HTML normalization reinterpret following text as attributes. Reachability requires an application to execute such a template with empty input; injected attributes can alter rendered tag behavior.

The record

CVE
CVE-2023-29400
Published
May 11, 2023
Updated
Jan 24, 2025
Vendor
Go standard library
Product
html/template
Classifications
CWE-94, CWE-74
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

7.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
7.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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')
CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

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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