What is CVE-2026-39823?

CVE-2026-39823 is a medium-severity vulnerability in Golang Go, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-05-07.

How severe is CVE-2026-39823?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Golang Go

CVE-2026-39823

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.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-05-07 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (24.0th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 24th percentile — 24.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000

Affected products

Golang Go
Go Standard Library Html/template — versions 0, 1.26.0-0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

go.dev/issue/78913 (Issue Tracking)
go.dev/cl/769920 (Patch)
groups.google.com/g/golang-announce/c/qcCIEXso47M (Release Notes)
pkg.go.dev/vuln/GO-2026-4982 (Vendor Advisory)

Frequently asked questions

What is CVE-2026-39823?: CVE-2026-39823 is a medium-severity vulnerability in Golang Go, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-05-07.
How severe is CVE-2026-39823?: Medium severity. CVSS v3 base score is 6.1 out of 10.