Saint Opossum, Who Played Dead Between TLS and Plaintext

Patron of protocols with opportunistic TLS, half-way upgrades, and those who mix cipher and plaintext.

Life

In 2025 researchers revealed the Opossum Attack (CVE-2025-49812), striking protocols that can switch from plaintext to TLS, such as HTTP with the RFC 2817 upgrade offered by Apache, and various mail and file-transfer protocols. A man in the middle could desync what the two parties believed they had negotiated, confusing the messages before and after the upgrade. Like the opossum playing dead, the traffic looked protected while it was already compromised.

Prayer

O Saint Opossum, who feigns security while opening a breach, teach our protocols never to mix plaintext and cipher. Amen.

How to celebrate

Celebrated by preferring implicit TLS over opportunistic TLS and updating servers that still accept the half-way upgrade.

Who plays dead throws off the guard.