dbcve.org
NetApplication · Golang

CVE-2026-27136

MEDIUM · 6.1 CVSS v3.1 Published 2026-05-22
Fix available
A fix is available. Upgrade to 0.55.0 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This is a HTML parsing vulnerability where specially crafted HTML input creates an unexpected DOM tree structure when rendered, allowing XSS attacks to bypass sanitization filters. The vulnerability exists in the rendering pipeline when applications parse and render user-supplied HTML content.

MitigationApplications should update to patched versions of their rendering libraries and implement additional output encoding or stricter sanitization to prevent XSS attacks via malformed HTML trees.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
NetApplication
Affected:< 0.55.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed Golang Net version
    Run 'go list -m all | grep golang.org/x/net' or inspect your go.mod file for the golang.org/x/net module version
    Affected if The version listed is below 0.55.0 (e.g., 0.54.0, 0.53.0, etc.)
  2. Determine if HTML parsing from untrusted sources occurs
    Search your codebase for usage of golang.org/x/net/html package functions such as Parse, ParseFragment, or any DOM rendering functions that process HTML input
    Affected if Your code imports and uses golang.org/x/net/html to parse or render HTML content from users or external sources
  3. Identify if content is rendered to browsers after parsing
    Check if parsed HTML is served or rendered in a web context (e.g., served via net/http, used in templates, or returned as HTTP responses)
    Affected if Parsed HTML output is returned to clients or rendered in browser contexts where the mutation could result in script execution
  4. Review HTML sanitization logic in use
    Inspect any sanitizer usage (such as bluemonday, go-html-sanitize, or custom sanitization) that processes HTML before rendering
    Affected if The sanitizer does not account for mXSS/mutation vectors or was not designed to handle the specific parsing discrepancies between the sanitizer and browser rendering engines

You are affected if you are using golang.org/x/net version below 0.55.0 and your application parses untrusted HTML content using the net/html package and renders it to browsers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.55.0 or later
Fixed in 0.55.0
Interim mitigation

Applications should update to patched versions of their rendering libraries and implement additional output encoding or stricter sanitization to prevent XSS attacks via malformed HTML trees.

Recommended fix Moderate confidence

0.55.0

  1. Upgrade the Net package to version 0.55.0 or later by running: go get github.com/go hamlet[REDACTED]@v0.55.0 or go get -u github.com/go hamlet[REDACTED]@latest
  2. After upgrading, run go mod tidy to update go.mod and go.sum
  3. Rebuild and test your application to ensure the upgrade does not break existing functionality
  4. If using go.sum, verify the new version is properly recorded

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Net Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,224.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-27136 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data