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php · symfony/mailomat-mailerHeads-up

symfony/mailomat-mailer enforces SHA-256 HMAC signature validation

MailomatRequestParser::validateSignature() now requires the signature header to be of the form sha256=<hex> and verifies the signature with HMAC-SHA256 using a constant-time comparison.

16 Jun 2026Read 1 minSeverity: schedule it

What changed

MailomatRequestParser::validateSignature() now requires the signature header to be of the form sha256=<hex> and verifies the signature with HMAC-SHA256 using a constant-time comparison. Any other algorithm is rejected.

Who it affects

Users of symfony/mailomat-mailer who use the Mailomat webhook receiver.

What to do today

Update to the patched version of symfony/mailomat-mailer (branch 7.4, 8.0, or 8.1) to enforce SHA-256 HMAC validation.

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