CVE-2026-39826 Escaper bypass leads to XSS in html/template
A flaw in Go's html/template package allows XSS when script tags have empty or whitespace-only type attributes, enabling malicious script 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-2026-39826?
CVE-2026-39826 is a medium-severity cross-site scripting vulnerability in Golang Go, published on 7 May 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
If a trusted template author were to write a <script> tag containing an empty 'type' attribute or a 'type' attribute with an ASCII whitespace, the execution of the template would incorrectly escape any data passed into the <script> block.
Weakness: CWE-116
Which versions are affected by CVE-2026-39826?
2 open source packages ship an affected version, including golang and stdlib. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
golang Bitnami | All versions | 1.25.10, 1.26.3 |
stdlib Go | All versions | 1.25.10, 1.26.3 |
Products include Golang Go.
How do I fix CVE-2026-39826?
Upgrade golang to a fixed version for your release line: 1.25.10 or 1.26.3.
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-2026-39826 being exploited?
There is no known exploitation of CVE-2026-39826 in the wild and no public exploit code.
Other vulnerabilities in Golang Go
- CVE-2020-0601 Microsoft Windows CryptoAPI Spoofing
- CVE-2026-27143 Missing bound checks can lead to memory corruption in safe Go in cmd/compile
- CVE-2024-24790 Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip
- CVE-2023-39320 Arbitrary code execution via go.mod toolchain directive in cmd/go
- CVE-2023-24540 Improper handling of JavaScript whitespace in html/template
Sources
Also known as AZL-98976, BELL-CVE-2026-39826, BIT-golang-2026-39826, CLEANSTART-2026-BD94423, CLEANSTART-2026-CS99408, CLEANSTART-2026-DF36684 and 795 more.