CVE-2026-47345: Typo3/html sanitizer Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-p5j5-4j3q-8mq8
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CWE-79
Published
Advisory Summary

CVE-2026-47345 is a MODERATE cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Typo3/html sanitizer libraries in the Packagist ecosystem. The issue involves typo3 html sanitizer allows cross-site scripting. Remediation is available by upgrading affected packages to version 2.3.2.

CVE-2026-47345 at a Glance

CVE Identifier CVE-2026-47345
GHSA Identifier GHSA-p5j5-4j3q-8mq8
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Typo3/html sanitizer
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-47345

To remediate this vulnerability, upgrade all affected Typo3/html sanitizer dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

typo3/html-sanitizer fixed: 2.3.2 
Upgrade typo3/html-sanitizer to 2.3.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for typo3/html-sanitizer

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-47345, inspect your project dependencies for Typo3/html sanitizer:

inspect dependencies for typo3/html-sanitizer

Analyze the terminal output to locate any version of Typo3/html sanitizer in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.3.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Typo3/html sanitizer, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Namespace attributes are not encoded correctly during HTML serialization. This allows bypassing the cross-site scripting prevention mechanism of `typo3/html-sanitizer` before version 2.3.2. Credits to Doyensec in collaboration with Claude and Anthropic Research for reporting this vulnerability.

CVE-2026-47345 Affected Typo3/html sanitizer Versions

1 component(s)
Fixed Versions:
2.3.2
Product / Package Ecosystem Affected Versions Fixed Version
typo3/html-sanitizer
 Packagist
< 2.3.2
2.3.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/TYPO3/html-sanitizer/security/advisories/GHSA-p5j5-4j3q-8mq8
NVD — CVE-2026-47345 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-47345
Security Fix Commit FIX COMMIT
https://github.com/TYPO3/html-sanitizer/commit/8b5d0be44ded457ca993ec9ca93d859941c63764
Typo3/html sanitizer Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/typo3/html-sanitizer/CVE-2026-47345.yaml
Typo3/html sanitizer Source Repository REPOSITORY
https://github.com/TYPO3/html-sanitizer
Typo3/html sanitizer Security Information SECURITY
https://typo3.org/security/advisory/typo3-core-sa-2026-006

Frequently Asked Questions

What is CVE-2026-47345?
CVE-2026-47345 is a security vulnerability in Typo3/html sanitizer involving TYPO3 HTML Sanitizer allows Cross-site Scripting under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Typo3/html sanitizer versions are affected?
Affected versions include releases prior to 2.3.2 across affected packages: typo3/html-sanitizer.
What version fixes CVE-2026-47345?
Upgrading to 2.3.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is typo3/html-sanitizer affected?
Yes, typo3/html-sanitizer is affected in releases prior to 2.3.2. Upgrade your dependency to 2.3.2 or later.
What CWE is associated with CVE-2026-47345?
CVE-2026-47345 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check Packagist dependencies for CVE-2026-47345?
Run the dependency tree command: 'inspect dependencies for typo3/html-sanitizer'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-p5j5-4j3q-8mq8",
  "modified" : "2026-06-12T20:07:46Z",
  "published" : "2026-06-12T20:07:46Z",
  "aliases" : [ "CVE-2026-47345" ],
  "summary" : "TYPO3 HTML Sanitizer allows Cross-site Scripting",
  "details" : "Namespace attributes are not encoded correctly during HTML serialization. This allows bypassing the cross-site scripting prevention mechanism of `typo3/html-sanitizer` before version 2.3.2.\n\nCredits to Doyensec in collaboration with Claude and Anthropic Research for reporting this vulnerability.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "typo3/html-sanitizer"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.3.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/TYPO3/html-sanitizer/security/advisories/GHSA-p5j5-4j3q-8mq8"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-47345"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/TYPO3/html-sanitizer/commit/8b5d0be44ded457ca993ec9ca93d859941c63764"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/typo3/html-sanitizer/CVE-2026-47345.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/TYPO3/html-sanitizer"
  }, {
    "type" : "WEB",
    "url" : "https://typo3.org/security/advisory/typo3-core-sa-2026-006"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-12T20:07:46Z",
    "nvd_published_at" : "2026-06-08T20:17:01Z"
  }
}