What’s Vulnerable › Vulnerabilities

CVE-2026-45753: Symfony: HtmlSanitizer UrlAttributeSanitizer Omits action/formaction/poster/cite — javascript: URI Survives Sanitization (XSS)

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-14 · updated 2026-07-15
• Weakness: CWE-79

Description

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. From 6.1.0-BETA1 until 6.4.40, 7.4.12, and 8.0.12, UrlAttributeSanitizer::getSupportedAttributes() omits URL-valued attributes including action, formaction, poster, and cite, so configurations that admit those attributes can leave javascript: URIs unsanitized and enable XSS when the resulting HTML is rendered or a victim submits a form or clicks a button. This issue is fixed in versions 6.4.40, 7.4.12, and 8.0.12.

Affected products

• symfony: from 6.1.0 before 6.4.40; from 7.0.0 before 7.4.12; from 8.0.0 before 8.0.12 — fixed in 6.4.40, 7.4.12, 8.0.12

How to fix

Upgrade to a fixed version: symfony 6.4.40, 7.4.12, 8.0.12. Check the vendor advisory for mitigations.

References

• https://github.com/symfony/symfony/commit/487728e7e180a674a6d4c01bd0cb56161cc441b7
• https://github.com/symfony/symfony/releases/tag/v6.4.40
• https://github.com/symfony/symfony/releases/tag/v7.4.12
• https://github.com/symfony/symfony/releases/tag/v8.0.12
• https://github.com/symfony/symfony/security/advisories/GHSA-hhg7-c65m-h7ff

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