CVE-2026-45753: symfony XSS — Fix

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.

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CVSS v3.1 Score

6.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS — Exploit Prediction

0.0030

Probability of exploitation

0.22%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

CWE-184 CWE-184

Affected Products

Vendor	Product	Versions
sensiolabs	symfony	6.1.0 — 6.4.40
sensiolabs	symfony	7.0.0 — 7.4.12
sensiolabs	symfony	8.0.0 — 8.0.12

References

Advisories & Patches

https://github.com/symfony/symfony/commit/487728e7e180a674a6d4c01bd0cb56161cc441b7 https://github.com/symfony/symfony/security/advisories/GHSA-hhg7-c65m-h7ff

Other References

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

Frequently Asked Questions

What is CVE-2026-45753? +

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. It has a CVSS v3.1 base score of 6.1 (MEDIUM).

How severe is CVE-2026-45753? +

CVE-2026-45753 has a CVSS v3.1 score of 6.1 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0030, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-45753? +

CVE-2026-45753 affects products from sensiolabs, specifically: symfony. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-45753? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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