---
description: Cloudflare IPsec now supports the IKE_SA_INIT_FULL_TRANSCRIPT_AUTH extension to prevent quantum downgrade attacks on IKEv2 tunnels.
title: IPsec downgrade protection (beta)
image: https://developers.cloudflare.com/changelog/post/2026-07-08-ipsec-downgrade-protection/og.png?v=d15eaf7581dd67ee
---

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July 8, 2026

## IPsec downgrade protection (beta)

[Cloudflare One](https://developers.cloudflare.com/cloudflare-one/) [Cloudflare WAN](https://developers.cloudflare.com/cloudflare-wan/)

Copy as Markdown| [View as Markdown](https://developers.cloudflare.com/changelog/post/2026-07-08-ipsec-downgrade-protection/index.md)| [Agent setup](https://developers.cloudflare.com/agent-setup/)

Cloudflare IPsec now supports the [`IKE_SA_INIT_FULL_TRANSCRIPT_AUTH` ↗︎](https://datatracker.ietf.org/doc/draft-ietf-ipsecme-ikev2-downgrade-prevention/) IKEv2 extension to protect against downgrade attacks on IPsec tunnels.

IKEv2's original authentication design has each endpoint sign only its own outbound messages, not the full handshake transcript. A quantum-capable [on-path attacker ↗︎](https://www.cloudflare.com/learning/security/threats/on-path-attack/) can exploit this to bypass post-quantum key exchange by downgrading the connection to classical cryptography. The `IKE_SA_INIT_FULL_TRANSCRIPT_AUTH` extension addresses this by having both peers sign the entire handshake transcript during the authentication exchange, preventing an attacker from manipulating the negotiation without detection.

Key details:

- Available in beta for Cloudflare WAN and Magic Transit IPsec tunnels.
- Cloudflare sends the `IKE_SA_INIT_FULL_TRANSCRIPT_AUTH` notification unconditionally as a responder when the feature flag is enabled.
- Both the initiator (your device) and responder (Cloudflare) must support the extension for downgrade protection to be effective.
- This feature is currently gated by a per-account feature flag. Contact your account team to turn it on.

Refer to [Downgrade protection](https://developers.cloudflare.com/cloudflare-wan/reference/gre-ipsec-tunnels/#improved-downgrade-protection-beta) for more details.

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