CVE-2026-39826Network attack vector

Cross-site scripting via misclassified script type

Published May 7, 2026 · Updated May 7, 2026

Cross-site scripting in Go html/template before 1.25.10 and 1.26.0-0 through 1.26.2 allows attackers to execute script in rendered pages. The isJSType check misclassifies an empty type value or one containing ASCII whitespace, so Template.Execute and Template.ExecuteTemplate select the wrong escaping context for untrusted data inside a script element. A trusted template author must create the affected script tag, and a user must load output containing attacker-controlled data; the resulting script can read or modify data accessible to that page.

CVSS severity6.1
Medium
EPSS probability0.37%
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 html/template before 1.25.10 and 1.26.0-0 through 1.26.2 allows attackers to execute script in rendered pages. The isJSType check misclassifies an empty type value or one containing ASCII whitespace, so Template.Execute and Template.ExecuteTemplate select the wrong escaping context for untrusted data inside a script element. A trusted template author must create the affected script tag, and a user must load output containing attacker-controlled data; the resulting script can read or modify data accessible to that page.

The record

CVE
CVE-2026-39826
Published
May 7, 2026
Updated
May 7, 2026
Vendor
Go
Product
html/template
Classifications
CWE-116, CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 7, 2026CVE publishedPublication date reported by the CVE source.
  2. May 7, 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=0 <1.25.10
  2. Affected versionversion=1.26.0-0 <1.26.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Go · html/templateversion=0 <1.25.10; version=1.26.0-0 <1.26.3

Published CVSS scores

6.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

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-116Improper Encoding or Escaping of Output
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

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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