CVE-2026-45065: Symfony: UrlGenerator Route-Requirement Bypass via Unanchored Regex Alternation → Off-Site //host URL Injection

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-185

Description

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 5.4.52, 6.4.40, 7.4.12, and 8.0.12, UrlGenerator validates route parameters against a pattern built as ^ plus the raw requirement plus $; with ungrouped alternations, middle alternatives match as unanchored substrings, allowing a value such as //evil.com to satisfy a common locale requirement and generate a protocol-relative off-site URL. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.

Affected products

symfony: before 5.4.52; from 6.0.0 before 6.4.40; from 7.0.0 before 7.4.12; from 8.0.0 before 8.0.12 — fixed in 5.4.52, 6.4.40, 7.4.12, 8.0.12
Packagist Symfony/Routing: before 5.4.52; from 6.0.0 before 6.4.40; from 7.0.0 before 7.4.12; from 8.0.0 before 8.0.12; 2.0.4, 2.0.5, 2.0.6, 2.0.7, v2.0.10, v2.0.12 (+610) — fixed in 5.4.52, 6.4.40, 7.4.12, 8.0.12
Packagist Symfony/Symfony: before 5.4.52; from 6.0.0 before 6.4.40; from 7.0.0 before 7.4.12; from 8.0.0 before 8.0.12; 2.0.4, 2.0.5, 2.0.6, 2.0.7, v2.0.10, v2.0.11 (+696) — fixed in 5.4.52, 6.4.40, 7.4.12, 8.0.12

How to fix

Upgrade to a fixed version: symfony 5.4.52, 6.4.40, 7.4.12, 8.0.12; Packagist Symfony/Routing 5.4.52, 6.4.40, 7.4.12, 8.0.12; Packagist Symfony/Symfony 5.4.52, 6.4.40, 7.4.12, 8.0.12. Check the vendor advisory for mitigations.

References

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