CVE-2026-39823: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in Go standard library html/template
CVE-2026-27142 fixed a vulnerability in which URLs were not correctly escaped inside of a <meta> tag's <content> attribute. If the URL content were to insert ASCII whitespaces around the '=' rune inside of the <content> attribute, the escaper would fail to similarly escape it, leading to XSS.
AI Analysis
Technical Summary
This vulnerability involves improper neutralization of input during web page generation in the Go standard library's html/template package. Specifically, URLs within a <meta> tag's <content> attribute are not correctly escaped if ASCII whitespaces surround the '=' rune, causing the escaping mechanism to fail and enabling cross-site scripting (CWE-79). The issue was related to a previous CVE-2026-27142 fix but remains present in affected versions up to 1.26.0-0. No CVSS score or remediation level is currently available.
Potential Impact
The vulnerability allows an attacker to inject malicious scripts via specially crafted URLs in the <meta> tag's <content> attribute, potentially leading to cross-site scripting attacks. This can result in client-side script execution in the context of the vulnerable application, which may compromise user data or session integrity. However, no known exploits are currently reported in the wild.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, users should exercise caution when processing untrusted input in the html/template package, particularly in <meta> tag content attributes. Monitor official Go project communications for updates on patches or workarounds.
CVE-2026-39823: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in Go standard library html/template
Description
CVE-2026-27142 fixed a vulnerability in which URLs were not correctly escaped inside of a <meta> tag's <content> attribute. If the URL content were to insert ASCII whitespaces around the '=' rune inside of the <content> attribute, the escaper would fail to similarly escape it, leading to XSS.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves improper neutralization of input during web page generation in the Go standard library's html/template package. Specifically, URLs within a <meta> tag's <content> attribute are not correctly escaped if ASCII whitespaces surround the '=' rune, causing the escaping mechanism to fail and enabling cross-site scripting (CWE-79). The issue was related to a previous CVE-2026-27142 fix but remains present in affected versions up to 1.26.0-0. No CVSS score or remediation level is currently available.
Potential Impact
The vulnerability allows an attacker to inject malicious scripts via specially crafted URLs in the <meta> tag's <content> attribute, potentially leading to cross-site scripting attacks. This can result in client-side script execution in the context of the vulnerable application, which may compromise user data or session integrity. However, no known exploits are currently reported in the wild.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, users should exercise caution when processing untrusted input in the html/template package, particularly in <meta> tag content attributes. Monitor official Go project communications for updates on patches or workarounds.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Go
- Date Reserved
- 2026-04-07T18:13:03.527Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69fcf0c1cbff5d86102bd5cb
Added to database: 5/7/2026, 8:06:25 PM
Last enriched: 5/7/2026, 8:21:59 PM
Last updated: 5/8/2026, 8:48:58 PM
Views: 12
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