CVE-2026-48761
Symfony: HtmlSanitizer UrlAttributeSanitizer Misses URL Attributes on <object>, <applet>, <iframe>, <img> and the URL Inside <meta http-equiv="refresh"> content
Blast Radius
symfony/html-sanitizer🐘symfony/html-sanitizer🐘symfony/html-sanitizer🐘symfony/symfony🐘symfony/symfony🐘symfony/symfonyReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Symfony is a PHP framework for web and console applications and a set of reusable PHP components. From 6.1.0 until 6.4.41, 7.4.13, and 8.0.13, UrlAttributeSanitizer::getSupportedAttributes() omitted URL-bearing attributes on <object>, <applet>, <iframe>, and <img>, and <meta http-equiv="refresh"> URLs inside content bypassed URL sanitization, allowing explicitly enabled elements or attributes to pass javascript: and similar payloads into sanitized output. This issue is fixed in versions 6.4.41, 7.4.13, and 8.0.13.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | symfony/html-sanitizer | ≥ 6.1.0&&< 6.4.41 | 6.4.41 |
| 🐘Packagist | symfony/html-sanitizer | ≥ 7.0.0&&< 7.4.13 | 7.4.13 |
| 🐘Packagist | symfony/html-sanitizer | ≥ 8.0.0&&< 8.0.13 | 8.0.13 |
| 🐘Packagist | symfony/symfony | ≥ 6.1.0&&< 6.4.41 | 6.4.41 |
| 🐘Packagist | symfony/symfony | ≥ 7.0.0&&< 7.4.13 | 7.4.13 |
| 🐘Packagist | symfony/symfony | ≥ 8.0.0&&< 8.0.13 | 8.0.13 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/html-sanitizer. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update symfony/html-sanitizer to 6.4.41 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48761 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-48761 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-48761. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-48761 in your dependencies?
O3 detects CVE-2026-48761 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.