---
id: 1978
title: "What Application Developers Need To Know About TLS Early Data (0RTT)"
source_domain: blog.trailofbits.com
source_url: "https://blog.trailofbits.com/2019/03/25/what-application-developers-need-to-know-about-tls-early-data-0rtt/"
published_at: "2019-03-25T13:00:23Z"
tags: ["web-security", "tls", "tls13", "0rtt", "replay-attacks"]
phying_url: "https://phying.com/item/1978"
lang: en
---

# What Application Developers Need To Know About TLS Early Data (0RTT)

## Summary

TLS 1.3's 0-RTT early data enables replay attacks on apps lacking anti-replay defenses—upgrading TLS alone can introduce vulnerabilities. It covers mitigations at CDN, proxy, and application layers.

## Intelligence Metadata

- **Sources:** blog.trailofbits.com
- **Published:** 2019-03-25T13:00:23Z
- **Original:** https://blog.trailofbits.com/2019/03/25/what-application-developers-need-to-know-about-tls-early-data-0rtt/
- **Phying News:** https://phying.com/item/1978