Skip to main content
VulnerabilityPublished

CVE-2026-39823: Go standard library html/template · Cross-site Scripting

Affects Go standard library html/templateSource CVE Database V5

0
Compare

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

CVSS 3.1 base score
6.1Medium
How severe the flaw is on the 0–10 CVSS scale.
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:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 7 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
Go standard libraryhtml/templateAffected
  • >=1.26.0-0 <1.26.3
Fixed in
  • 1.26.3
Go standard libraryhtml/templateAffected
  • <1.25.10
Fixed in
  • 1.25.10
Gohtml/templatepkg:golang/html/templateOther threatsAffected
  • <1.25.10
  • >=1.26.0-0 <1.26.3
Fixed in
  • 1.25.10
  • 1.26.3
Gogithub.com/golang/go/html/templatepkg:golang/github.com/golang/go/html/templateOther threatsAffected
  • =0
  • =1.26.0-0
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.

References

Community reviews

Loading reviews…