CVE-2026-48747: symfony Signature Bypass — Fix

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.

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CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0020

Probability of exploitation

0.10%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-347 CWE-347

CWE-757 CWE-757

Affected Products

Vendor	Product	Versions
sensiolabs	symfony	7.2.0 — 7.4.13
sensiolabs	symfony	8.0.0 — 8.0.13

References

Advisories & Patches

https://github.com/symfony/symfony/commit/bdfe9fe0d94d33dfaca0bc2fe0b00b54767b0c88 https://github.com/symfony/symfony/security/advisories/GHSA-rrj9-5q2j-4gvr

Other References

https://github.com/symfony/symfony/releases/tag/v7.4.13 https://github.com/symfony/symfony/releases/tag/v8.0.13

Frequently Asked Questions

What is CVE-2026-48747? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-48747? +

CVE-2026-48747 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0020, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-48747? +

CVE-2026-48747 affects products from sensiolabs, specifically: symfony. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-48747? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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