Bypass of meta content URL escaping causes XSS in html/template (CVE-2026-39823) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-39823

Bypass of meta content URL escaping causes XSS in html/template

Answer in brief

CVE-2026-39823 records a Unknown severity vulnerability in Bypass of meta content URL escaping causes XSS in html/template. The current sources do not mark it as known exploited. The current feed maps stdlib (go). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published May 7, 2026Updated Aug 26, 2026Source checked Aug 26, 2026First seen by HOL Aug 8, 2026Material review Aug 26, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps stdlib (go). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
stdlibgo	>=0 <1.25.10 >=1.26.0-0 <1.26.3	1.25.10, 1.26.3

Recommended response

Check inventory. Check lockfiles and deployed manifests for stdlib.
Review the reported fix. Update stdlib to 1.25.10 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
May 7, 2026
Evidence: source:osv:source_dates:source-dates:record
Source modified
Aug 26, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Aug 8, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.