RFC 9851: TLS 1.2 is in Feature Freeze
RFC 9851<br>TLS 1.2 Frozen<br>July 2026
Salz & Aviram<br>Standards Track<br>[Page]
Stream:<br>Internet Engineering Task Force (IETF)<br>RFC:<br>9851<br>Category:<br>Standards Track<br>Published:
July 2026
ISSN:<br>2070-1721<br>Authors:
R. Salz
Akamai Technologies
N. Aviram
RFC 9851
TLS 1.2 is in Feature Freeze
Abstract
Use of TLS 1.3, which fixes some known deficiencies in TLS 1.2, is<br>growing. This document specifies that no changes will be approved<br>for TLS 1.2 outside of urgent security fixes (as determined by<br>TLS Working Group consensus), new TLS Exporter Labels, and<br>new Application-Layer Protocol Negotiation (ALPN) Protocol IDs.<br>This applies to TLS only; it does not apply to DTLS (in<br>any DTLS version).¶
Status of This Memo
This is an Internet Standards Track document.¶
This document is a product of the Internet Engineering Task Force<br>(IETF). It represents the consensus of the IETF community. It has<br>received public review and has been approved for publication by<br>the Internet Engineering Steering Group (IESG). Further<br>information on Internet Standards is available in Section 2 of<br>RFC 7841.¶
Information about the current status of this document, any<br>errata, and how to provide feedback on it may be obtained at<br>https://www.rfc-editor.org/info/rfc9851.¶
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the<br>document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal<br>Provisions Relating to IETF Documents<br>(https://trustee.ietf.org/license-info) in effect on the date of<br>publication of this document. Please review these documents<br>carefully, as they describe your rights and restrictions with<br>respect to this document. Code Components extracted from this<br>document must include Revised BSD License text as described in<br>Section 4.e of the Trust Legal Provisions and are provided without<br>warranty as described in the Revised BSD License.¶
Table of Contents
1. Introduction
TLS 1.3 [TLS13] fixes most known deficiencies with TLS 1.2 [TLS12] and its use is growing. Some examples of the fixes include<br>encrypting more of the traffic so that it is not readable by outsiders and<br>removing most cryptographic primitives that are now considered weak. Importantly, TLS<br>1.3 enjoys robust security proofs.¶
Both versions have several extension points. Items like new cryptographic<br>algorithms, new supported groups (formerly "named curves"), etc., can be<br>added without defining a new protocol. This document specifies that no changes will be approved for TLS 1.2 outside of<br>urgent security fixes (as determined by TLS Working Group consensus) and the exceptions listed in Section 4.¶
This applies to TLS only. As such, it does not apply to<br>DTLS, in any DTLS version.¶
2. Implications for Post-Quantum Cryptography (PQC)
Cryptographically relevant quantum computers, once available, are likely to<br>greatly lessen the time and effort needed to break<br>RSA, finite-field-based Diffie-Hellman (FFDH), or Elliptic Curve Cryptography (ECC) which are currently used in TLS.<br>In 2016, the US National Institute of Standards and Technology (NIST) started a<br>multi-year effort to standardize algorithms that will be "safe"<br>once quantum computers are feasible [PQC]. Initial discussions in<br>the IETF community happened<br>around the same time [CFRGSLIDES].¶
In 2024, NIST released standards for [ML-KEM], [ML-DSA], and [SLH-DSA].<br>Many other countries and organizations are publishing their roadmaps,<br>including the multi-national standards organization ETSI [ETSI].¶
While the industry was waiting for NIST to finish standardization, the<br>IETF has had several efforts underway.<br>A working group was formed in early 2023 to work on the use of Post-Quantum Cryptography (PQC) in IETF protocols<br>[PQUIPWG].<br>Several other working groups, including TLS [TLSWG],<br>are working on<br>specifications to support hybrid algorithms and identifiers, for use during a<br>transition from classic to a post-quantum world.¶
It is important to note that effort within the TLS Working Group is focused exclusively on TLS 1.3 or later.<br>Put bluntly, PQC for<br>TLS 1.2 will not be specified (see Section 4) at any time; anyone wishing<br>to deploy PQC should expect to use TLS 1.3.¶
3. Security Considerations
This entire document is about security and provides post-quantum security concerns<br>as an additional reason to upgrade to TLS 1.3.¶
4. IANA Considerations
No TLS registries [TLS13REG] are being closed by this document.<br>Rather, this document modifies the instructions to IANA and the TLS<br>Designated Experts to constrain the type of entries that can be added to existing<br>registries.¶
This document does not introduce any new limitations on the registrations for either of<br>the following two registries:¶
TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs¶
TLS Exporter Labels¶
The following note has been added to the other TLS registries:¶
Any TLS entry added after the IESG approves publication of RFC 9851<br>is intended for...