CVE-2026-39823: Go standard library html/template · Cross-site Scripting
Affects Go standard library html/templateSource CVE Database V5
Not known to be exploited · CVSS 6.1 Medium : upgrade to 1.26.3 or 1.25.10 when convenient.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 24% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.26.3, 1.25.10
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 7 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade Go standard library html/template to 1.26.3 or 1.25.10.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Go standard libraryhtml/template | Affected
| Fixed in
|
| Go standard libraryhtml/template | Affected
| Fixed in
|
Gohtml/templatepkg:golang/html/templateOther threats | Affected
| Fixed in
|
Gogithub.com/golang/go/html/templatepkg:golang/github.com/golang/go/html/templateOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, users should carefully review usage of the html/template package with respect to URL escaping in <meta> tags and consider applying manual input validation or escaping workarounds if feasible.
Description
CVE-2026-39823 is a medium severity cross-site scripting (XSS) vulnerability in the Go standard library's html/template package. The issue arises from improper escaping of URLs within a <meta> tag's content attribute when ASCII whitespaces surround the '=' character, which allows partial bypass of escaping. This affects Go versions up to 1.26.0-0.