Interpretation Conflict in Symfony - CVE-2026-45066
Published: May 21, 2026
Vulnerability identifier: #VU132069
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-45066
CWE-ID: CWE-436
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 bypass URL allowlist restrictions.
The vulnerability exists due to interpretation conflict in UrlSanitizer::parse() when parsing crafted URLs with backslashes or abnormal slash counts after special schemes. A remote attacker can supply a specially crafted URL to bypass URL allowlist restrictions.
The issue arises from differences between RFC-3986 parsing on the server side and WHATWG URL parsing in browsers.
How to mitigate CVE-2026-45066
Install security update from vendor's website.