What’s Vulnerable › Vulnerabilities

CVE-2019-18887: Symfony Http-Kernel has non-constant time comparison in UriSigner

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-11-21 · updated 2026-06-17
• Weakness: CWE-203

Description

An issue was discovered in Symfony 2.8.0 through 2.8.50, 3.4.0 through 3.4.34, 4.2.0 through 4.2.11, and 4.3.0 through 4.3.7. The UriSigner was subject to timing attacks. This is related to symfony/http-kernel.

Affected products

• Fedoraproject Fedora: 30, 31
• symfony: from 2.8.0 through 2.8.50; from 3.4.0 through 3.4.34; from 4.2.0 through 4.2.11; from 4.3.0 through 4.3.7
• Packagist Symfony/Http-Kernel: from 2.2.0 before 2.8.52; from 3.0.0 before 3.4.35; from 4.0.0 before 4.2.12; from 4.3.0 before 4.3.8; v2.2.0, v2.2.1, v2.2.10, v2.2.11, v2.2.2, v2.2.3 (+362) — fixed in 2.8.52, 3.4.35, 4.2.12, 4.3.8
• Packagist Symfony/Symfony: from 2.2.0 before 2.8.52; from 3.0.0 before 3.4.35; from 4.0.0 before 4.2.12; from 4.3.0 before 4.3.8; v2.2.0, v2.2.1, v2.2.10, v2.2.11, v2.2.2, v2.2.3 (+365) — fixed in 2.8.52, 3.4.35, 4.2.12, 4.3.8

How to fix

Upgrade to a fixed version: Packagist Symfony/Http-Kernel 2.8.52, 3.4.35, 4.2.12, 4.3.8; Packagist Symfony/Symfony 2.8.52, 3.4.35, 4.2.12, 4.3.8. Check the vendor advisory for mitigations.

References

• https://github.com/symfony/symfony/releases/tag/v4.3.8
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DZNXRVHDQBNZQUCNRVZICPPBFRAUWUJX/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UED22BOXTL2SSFMGYKA64ZFHGLLJG3EA/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VXEAOEANNIVYANTMOJ42NKSU6BGNBULZ/
• https://symfony.com/blog/cve-2019-18887-use-constant-time-comparison-in-urisigner
• https://symfony.com/blog/symfony-4-3-8-released
• https://github.com/symfony/symfony/releases/tag/v4.3.8
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DZNXRVHDQBNZQUCNRVZICPPBFRAUWUJX/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UED22BOXTL2SSFMGYKA64ZFHGLLJG3EA/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VXEAOEANNIVYANTMOJ42NKSU6BGNBULZ/
• https://symfony.com/blog/cve-2019-18887-use-constant-time-comparison-in-urisigner
• https://symfony.com/blog/symfony-4-3-8-released

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