EUVD-2026-384746

fkie_cve-2026-107380

savg-sanitizer is a PHP SVG/XML sanitizer. Prior to 1.0.0, svg-sanitizer's isHrefSafeValue() validates an SVG href after XML DTD entity expansion, but saveXML() serializes the original entity reference after removing the DTD declaration. A crafted entity such as Tab can appear to the sanitizer as a safe fragment prefix while HTML5 Named Character Reference resolution during inline HTML rendering later converts the surviving reference to whitespace, exposing a javascript: URL. When an application embeds the sanitized SVG inline, a user who activates the link can cause script to execute in the embedding page's origin. This issue is fixed in version 1.0.0.

GHSA-9rjx-3jch-6vjf — enshrined/svg-sanitize: Stored XSS via DTD Entity / HTML5 Named Character Reference Collision

Affected: Packagist: enshrined/svg-sanitize

## Summary

A crafted SVG bypasses `enshrined/svg-sanitize`'s href validation and delivers a `javascript:` URL through the sanitizer unchanged. The bypass exploits a semantic mismatch between XML entity resolution (used during sanitization) and HTML5 Named Character Reference resolution (used by the browser when the SVG is rendered inline).

**This is a logic bug in svg-sanitize. It does NOT depend on any PHP ext/dom bug — it works on any PHP version.**

**Affected installations:** - **enshrined/svg-sanitize:** 45.2M Packagist downloads, 1.3M/month, 90+ dependents - **WordPress Safe SVG plugin:** 1M+ active installs (inline SVG rendering via themes) - **TYPO3, Drupal** and 90+ other Packagist dependents

## Vulnerability Details

### Mechanism

1. Attacker defines a DTD entity whose name collides with an HTML5 Named Character Reference: ```xml <!ENTITY Tab "#"> ``` In XML, `&Tab;` expands to the literal string `"#"` (from the DTD definition). In HTML5, `&Tab;` is a Named Character Reference that resolves to U+0009 (TAB character).

2. The SVG uses this entity in an href: ```xml <a href="&Tab;javascript:alert(document.domain)"> ```

3. **During sanitization** (XML context): `&Tab;` → `"#"` → the sanitizer sees `href="#javascript:alert(document.domain)"` → starts with `#` → `isHrefSafeValue()` returns **TRUE** → passes through.

4. **Sanitizer output:** `saveXML()` outputs the entity reference `&Tab;` (not the expanded value), and strips the DOCTYPE dec…

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EUVD-2026-384746

fkie_cve-2026-107380

GHSA-9rjx-3jch-6vjf — enshrined/svg-sanitize: Stored XSS via DTD Entity / HTML5 Named Character Reference Collision