Symfony Blog

This week, Symfony released 36 security advisories and published security releases 5.4.52, 6.4.40, 7.4.12, 8.0.12, 8.1.0 BETA3 and Twig 3.26.0. We also published an article about how we used Claude Mythos to analyze the Symfony and Twig codebases and uncover many of these security issues. Lastly, we announced that the Symfony UX 2.x branch is now in security-fixes-only maintenance mode and shared more details about the SymfonyOnline June 2026 conference.

Mathias Arlaud will take a deep dive into the internals of Symfony's HTTP layer to explain the performance implications of how we handle responses and how to optimize your controllers for maximum efficiency

Symfony UX 2.x is now in security-only maintenance mode. Going forward, all new features and bug fixes will target Symfony UX 3.x, while security updates for 2.x will continue until January 1, 2027. Learn what this means for existing projects and why now is the right time to plan your upgrade to Symfony UX 3.x.

Symfony 8.1 improves Messenger with batch fetching, AMQP priorities, smarter retries, and configurable resets.

Claude Mythos Preview, Anthropic's unreleased model, audited Symfony and Twig code and reported 19 vulnerabilities. All of them turned out to be real.

Email Header Injection via Non-Token Characters in Mime Parameter Names

Johannes introduces Symfony Mate, an MCP server that exposes a curated, deterministic view of your running Symfony application (container, services, profiler, logs) to any MCP-aware client

SymfonyRuntime CVE-2024-50340 Patch Bypass: Web Requests Can Still Set APP_ENV/APP_DEBUG via parse_str/SAPI Argv Mismatch

JsonPath Evaluates Attacker-Controlled Regular Expressions in match()/search() Without Limits: ReDoS

Twilio Notifier Webhook Parser Never Verifies the X-Twilio-Signature HMAC: Unauthenticated Webhook Event Injection