Cross-site scripting in Symfony - CVE-2026-45753
Published: May 21, 2026
Vulnerability identifier: #VU132058
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Green
CVE-ID: CVE-2026-45753
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: SensioLabs
Affected software:
Symfony
Symfony
Detailed vulnerability description
The vulnerability allows a remote attacker to execute arbitrary script in the victim's browser.
The vulnerability exists due to incomplete neutralization of dangerous URL schemes in UrlAttributeSanitizer when sanitizing untrusted HTML with allowed action, formaction, poster, or cite attributes. A remote attacker can supply specially crafted HTML containing a javascript: URI to execute arbitrary script in the victim's browser.
User interaction is required in the action and formaction cases because the victim must submit the form or click the button, and exploitation requires a deliberately permissive sanitizer configuration that allows the affected attributes.
How to mitigate CVE-2026-45753
Install security update from vendor's website.