Symfony's HtmlSanitizer URL Attributes Pass Through BiDi Override Characters → Visual href Spoofing
Date: 2026-05
Affected: composer/symfony/symfony, composer/symfony/symfony, composer/symfony/symfony
Attack vector: phishing
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-45064
CWE: CWE-1007
CWE-451

### Description `Symfony\Component\HtmlSanitizer\TextSanitizer\UrlSanitizer::parse()` (used by `UrlSanitizer::sanitize()` and therefore by every `HtmlSanitizer` config that allows links or media) accepts URLs that contain Unicode explicit-direction BiDi formatting characters: U+202A–U+202E (LRE / RLE / PDF / LRO / RLO) and U+2066–U+2069 (LRI / RLI / FSI / PDI). These characters are passed through unchanged into the `href` / `src` attributes produced by `HtmlSanitizer`. When the resulting HTML is rendered in a browser, the override characters reverse or alter the visual ordering of the URL text, so the displayed link can differ arbitrarily from the actual destination: a classic visual-spoofing / phishing primitive against viewers of sanitized content. ### Resolution `UrlSanitizer::parse()` now rejects URLs containing the explicit-direction BiDi formatting code points (U+202A–U+202E, U+2066–U+2069) before invoking the underlying URL parser. As an unrelated companion fix in the same patch, spaces inside path/query/fragment are now percent-encoded rather than rejected outright, while spaces in the scheme/authority remain rejected by the post-encoding whitespace check. The patch for this issue is available [here](https://github.com/symfony/symfony/commit/743a435e948b897ef2b5564ac438d4beb95d2526) for branch 5.4. ### Credits Symfony would like to thank Himanshu Anand for reporting the issue and Nicolas Grekas for providing the fix.


Mitigations:

Architectural layers (MAESTRO):