Interpretation Conflict in Symfony - CVE-2026-45066
Published: May 21, 2026
Vulnerability identifier: #VU132069
CSH Severity: Medium
CVSS v4: 6.9 [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]
CVE-ID: CVE-2026-45066
CWE-ID: CWE-436
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
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.
Affected software
Symfony
Debian Linux
symfony (Debian package)
Debian Linux
symfony (Debian package)
How to mitigate CVE-2026-45066
Install security update from vendor's website.
Symfony - addressed in versions 6.4.40, 7.4.12, 8.0.12
symfony (Debian package) - update to 6.4.41+dfsg-0+deb13u1
symfony (Debian package) - update to 6.4.41+dfsg-0+deb13u1