CVE-2026-45065
Symfony has a UrlGenerator Route-Requirement Bypass via Unanchored Regex Alternation → Off-Site //host URL Injection
Description
### Description Symfony routes can declare a requirements regex per path parameter, e.g. a route `/{_locale}/blog` with `requirements: { _locale: 'en|fr|de' }`. The Twig `path()` / `url()` helpers (backed by `UrlGenerator`) validate supplied parameter values against that regex before building the URL. UrlGenerator constructs the validation pattern as `'#^'.$req.'$#'`, where `$req` is the raw requirement string. For a requirement expressed as an alternation, e.g. `_locale: 'ar|bg|...|vi|...|zh_CN'` (very common), `^` and `$` anchor only the first and last alternatives, so any middle alternative matches as an unanchored substring. A value like `/evil.com` satisfies the requirement (because it contains `vi`), and the generated path becomes `//evil.com/...`: a protocol-relative URL the browser navigates off-site. ### Resolution The `UrlGenerator` class now wraps the requirement in a non-capturing group so the `^` and `$` anchors apply to the whole alternation. The patch for this issue is available [here](https://github.com/symfony/symfony/commit/bcf487c22f3240ba994124e0e0fe8616f3cfc47a) for branch 5.4. ### Credits Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.
How to fix CVE-2026-45065
To remediate CVE-2026-45065, upgrade the affected package to a fixed version below.
- —no fix listed
- —upgrade to 5.4.52 or later
- —upgrade to 5.4.52 or later
Is CVE-2026-45065 being exploited?
No exploitation signal available. Neither CISA KEV nor a current EPSS score has been published for CVE-2026-45065.
Affected packages (3)
- from 0
- from 0, < 5.4.52
- from 0, < 5.4.52