CVE-2026-47345: TYPO3 html-sanitizer XSS bypass via incorrect namespace encoding

CVE-2026-47345 · Severity: medium · CVSS 4 · Published 2026-06-08

The TYPO3 HTML Sanitizer, a library used to clean and secure user-provided web content, contains a flaw in how it handles specific HTML attributes. An attacker could use this to bypass security filters and inject malicious scripts into web pages. If successful, this could lead to unauthorized actions being performed in the context of a user's session, such as stealing login tokens or redirecting users to malicious sites.

Technologies: typo3/html-sanitizer (Packagist). Vendors: Packagist, Typo3.

Quick answers

Is CVE-2026-47345 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-47345 being exploited in the wild.
How severe is CVE-2026-47345?
Medium severity, with a CVSS score of 4, published 8 June 2026.
Which products and versions are affected?
typo3/html-sanitizer (Packagist) < 2.3.2, ECOSYSTEM:introduced=0,fixed=2.3.2; Typo3 Html-Sanitizer < 2.3.2.
Is there a fix for CVE-2026-47345?
Yes. typo3/html-sanitizer (Packagist): upgrade to 2.3.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-47345 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-47345?
Check whether you run typo3/html-sanitizer (Packagist) or Typo3 Html-Sanitizer at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • typo3/html-sanitizer (Packagist): upgrade to 2.3.2 or later
    composer require typo3/html-sanitizer:^2.3.2

Technical details

A Cross-Site Scripting (XSS) vulnerability exists in typo3/html-sanitizer due to improper neutralization of namespace attributes during the HTML serialization process. The root cause is a failure to correctly encode these attributes, which allows an attacker to craft malicious payloads that bypass the sanitizer's intended security logic. The attack requires network access and low privileges, typically involving a victim interacting with a page containing the malicious input. This can result in a bypass of the library's XSS prevention mechanisms. The issue is fixed in version 2.3.2 by ensuring namespace attributes are properly encoded in the Serializer component.

Affected products

  • TYPO3 html-sanitizer < 2.3.2

Identifiers

  • CVE-2026-47345
  • GHSA-p5j5-4j3q-8mq8

Timeline

  • 2026-06-08: disclosed: Initial disclosure by TYPO3 and NVD publication
  • 2026-06-12: advisory: GitHub Advisory published

References

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