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Vulnerability · Published Jul 14, 2026 · Assigned by GitHub_M

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

Medium 6.3

In plain English

A medium-severity security flaw in mailomat-mailer from symfony. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 16% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.3Medium
Exploit odds (30 days)0.2%top 83.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:14symfony7.4.13+dfsg-1DEBIAN-CVE-2026-48747
Packagistsymfony/mailomat-mailer8.0.13GHSA-rrj9-5q2j-4gvr
Packagistsymfony/mailomat-mailer7.4.13GHSA-rrj9-5q2j-4gvr
Packagistsymfony/symfony7.4.13GHSA-rrj9-5q2j-4gvr
Packagistsymfony/symfony8.0.13GHSA-rrj9-5q2j-4gvr
Ubuntu:25.10symfonyno fix listedUBUNTU-CVE-2026-48747
Ubuntu:26.04:LTSsymfonyno fix listedUBUNTU-CVE-2026-48747
Ubuntu:26.10symfonyno fix listedUBUNTU-CVE-2026-48747

Affected products (as reported)

VendorProductVersions
symfony symfony >= 7.2.0, < 7.4.12>= 8.0.0-BETA1, < 8.0.13
symfony mailomat-mailer >= 7.2.0, < 7.4.12>= 8.0.0-BETA1, < 8.0.13

Weakness: CWE-347, CWE-757 · Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

References