CVE-2026-56858 Fix Javascript regexp context tracking in html/template
Attackers can inject arbitrary content via pathological inputs in Go's html/template, leading to Cross-Site Scripting (XSS) and potential code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-56858?
CVE-2026-56858 is a medium-severity cross-site scripting vulnerability in Go standard library html/template, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Previously, pathological inputs could close an unescaped '/' early, allowing for attack-controlled data to inject arbitrary content, potentially leading to XSS.
Weakness: CWE-79
Which versions are affected by CVE-2026-56858?
2 open source packages ship an affected version, including golang and stdlib.
| Package | Affected | Fixed in |
|---|---|---|
golang Bitnami | All versions | 1.25.13, 1.26.6, 1.27.0 |
stdlib Go | All versions | 1.25.13, 1.26.6, 1.27.0-rc.3 |
How do I fix CVE-2026-56858?
Upgrade golang to a fixed version for your release line: 1.25.13, 1.26.6 or 1.27.0.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-56858 being exploited?
There is no known exploitation of CVE-2026-56858 in the wild and no public exploit code.
Sources
Also known as AZL-96650, AZL-96674, AZL-98964, BELL-CVE-2026-56858, BIT-golang-2026-56858, CLEANSTART-2026-CR23307 and 2156 more.