CVE-2026-45066 in Symfony HTML Sanitizer
Symfony HTML Sanitizer can bypass allowed link or media host rules because some URLs are parsed differently than expected.
Quick answer
Symfony HTML Sanitizer should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- symfony/html-sanitizer >=6.1.0 <6.4.40, >=7.0.0 <7.4.12, and >=8.0.0 <8.0.12
Fixed versions
- symfony/html-sanitizer 6.4.40, 7.4.12, or 8.0.12
How to fix it
Update Symfony HTML Sanitizer. The old version can let unsafe input change how the app works.
- Update symfony/html-sanitizer to symfony/html-sanitizer 6.4.40, 7.4.12, or 8.0.12 with Composer.
- Run the app test suite.
- Clear Symfony cache and redeploy.
- Check logs for errors after release.
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Verify the fix
- Run composer show symfony/html-sanitizer and confirm the fixed version is installed.
- Retest the route, mailer, or sanitizer path that used the affected package.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-45066?
Symfony HTML Sanitizer versions listed as affected should be reviewed: symfony/html-sanitizer >=6.1.0 <6.4.40, >=7.0.0 <7.4.12, and >=8.0.0 <8.0.12.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.