What’s Vulnerable › Vulnerabilities

CVE-2026-48747: Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signature Algorithm Downgrade

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% 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-347

Description

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 7.4.13 and 8.0.13, MailomatRequestParser::validateSignature() parsed X-MOM-Webhook-Signature as algo=signature and passed the request-selected algorithm to hash_hmac(), allowing a signature algorithm downgrade instead of enforcing Mailomat's documented SHA-256 webhook signature. This issue is fixed in versions 7.4.13 and 8.0.13.

Affected products

• symfony: from 7.2.0 before 7.4.13; from 8.0.0 before 8.0.13 — fixed in 7.4.13, 8.0.13

How to fix

Upgrade to a fixed version: symfony 7.4.13, 8.0.13. Check the vendor advisory for mitigations.

References

• https://github.com/symfony/symfony/commit/bdfe9fe0d94d33dfaca0bc2fe0b00b54767b0c88
• https://github.com/symfony/symfony/releases/tag/v7.4.13
• https://github.com/symfony/symfony/releases/tag/v8.0.13
• https://github.com/symfony/symfony/security/advisories/GHSA-rrj9-5q2j-4gvr

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