RFC 9851

TLS 1.2 is in Feature Freeze

📅 published July 2026, from ietf

TLS 1.2 is in Feature Freeze 🎀

Okay bestie, here's the deets on RFC 9851 💅. It's a Standards Track doc from the Internet Engineering Task Force (IETF), published in July 2026, with ISSN 2070-1721. The authors are Rich Salz (Akamai Technologies) and Nimrod Aviram 🦋. Its header doesn't list anything it obsoletes or updates, so it's standing on its own ✨.

Abstract

Using TLS 1.3 is becoming the move 📈, and it fixes some known problems in TLS 1.2. This doc says that for TLS 1.2, nothing new gets approved except urgent security fixes (as decided by TLS Working Group consensus), new TLS Exporter Labels, and new Application-Layer Protocol Negotiation (ALPN) Protocol IDs 🔒. This only covers TLS, not DTLS, in any DTLS version 🙅‍♀️.

Status of This Memo

This is an Internet Standards Track document 🌸.

It's a product of the IETF and represents the consensus of the IETF community. It got public review and was approved for publication by the Internet Engineering Steering Group (IESG). For more on Internet Standards, check Section 2 of RFC 7841 📚.

For the current status, any errata, and where to send feedback, go to https://www.rfc-editor.org/info/rfc9851 🔗.

Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved 💜.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) as in effect on the date of publication. Please read these carefully, because they explain your rights and restrictions for this document 📜. Code Components pulled out of this document must include Revised BSD License text, as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as described in the Revised BSD License ⚖️.

Table of Contents

  • 1. Introduction
  • 2. Implications for Post-Quantum Cryptography (PQC)
  • 3. Security Considerations
  • 4. IANA Considerations
  • 5. References
    • 5.1. Normative References
    • 5.2. Informative References
  • Acknowledgments
  • Authors' Addresses

1. Introduction ✨

TLS 1.3 [TLS13] fixes most of the known problems with TLS 1.2 [TLS12], and people are adopting it more and more 🚀. Some of the upgrades are encrypting more of the traffic so outsiders can't read it, and dropping most of the cryptographic primitives that are now considered weak 🔐. Most importantly, TLS 1.3 has robust security proofs 💅.

Both versions have several extension points 🧩. Things like new cryptographic algorithms and new supported groups (formerly "named curves") can be added without defining a new protocol. This doc says no changes will be approved for TLS 1.2 except urgent security fixes (as decided by TLS Working Group consensus) and the exceptions listed in Section 4 🙌.

This only covers TLS, so it doesn't apply to DTLS, in any DTLS version 💖.

2. Implications for Post-Quantum Cryptography (PQC) 🔮

Once cryptographically relevant quantum computers are available, they'll likely make it way faster and easier to break RSA, finite-field-based Diffie-Hellman (FFDH), or Elliptic Curve Cryptography (ECC), which are all used in TLS right now 😱. In 2016, the US National Institute of Standards and Technology (NIST) kicked off a multi-year effort to standardize algorithms that will be "safe" once quantum computers are feasible [PQC]. The IETF community started talking about it around the same time [CFRGSLIDES].

In 2024, NIST released standards for [ML-KEM], [ML-DSA], and [SLH-DSA] 🎉. Lots of other countries and organizations are publishing their roadmaps too, including the multi-national standards organization ETSI [ETSI] 🌍.

While the industry was waiting for NIST to finish, the IETF had a bunch of efforts going 🛠️. A working group formed in early 2023 to look at using Post-Quantum Cryptography (PQC) in IETF protocols [PQUIPWG]. Several other working groups, including TLS [TLSWG], are writing specs for hybrid algorithms and identifiers, for the transition from classic crypto to a post-quantum world 🌈.

Important note, bestie: the TLS Working Group is focusing exclusively on TLS 1.3 or later 👑. Put bluntly, PQC for TLS 1.2 will not be specified (see Section 4) at any time 💀. Anyone who wants to deploy PQC should expect to use TLS 1.3 🫶.

3. Security Considerations 🔒

This entire document is about security 🛡️. It also gives post-quantum security concerns as an extra reason to upgrade to TLS 1.3 🚨.

4. IANA Considerations 📋

No TLS registries [TLS13REG] are being closed by this doc 🙅‍♀️. Instead, it changes the instructions to IANA and the TLS Designated Experts so they limit what kinds of entries can be added to the existing registries 🎯.

This doc doesn't add any new limits on registrations for these 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 is intended for TLS 1.3 or later, and makes no similar
|  requirement on DTLS.  Such entries should have an informal
|  indication like "For TLS 1.3 or later" in that entry, such as the
|  "Comment" column.

At the time of publication, the note has been added to these TLS registries 🗂️:

  • TLS Alerts
  • TLS Authorization Data Formats
  • TLS CachedInformationType Values
  • TLS Certificate Compression Algorithm IDs
  • TLS Certificate Status Types
  • TLS Certificate Types
  • TLS Cipher Suites
  • TLS ClientCertificateType Identifiers
  • TLS ContentType
  • TLS EC Curve Types
  • TLS EC Point Formats
  • TLS ExtensionType Values
  • TLS HandshakeType
  • TLS HashAlgorithm
  • TLS Heartbeat Message Types
  • TLS Heartbeat Modes
  • TLS KDF Identifiers
  • TLS PskKeyExchangeMode
  • TLS SignatureAlgorithm
  • TLS SignatureScheme
  • TLS Supplemental Data Formats (SupplementalDataType)
  • TLS Supported Groups
  • TLS UserMappingType Values

Any TLS registry created after this doc is approved for publication should say whether the actions defined here apply to it 🔍.

5. References 📚

5.1. Normative References

[TLS12]    Dierks, T. and E. Rescorla, "The Transport Layer Security
           (TLS) Protocol Version 1.2", RFC 5246,
           DOI 10.17487/RFC5246, August 2008,
           <https://www.rfc-editor.org/info/rfc5246>.

[TLS13]    Rescorla, E., "The Transport Layer Security (TLS) Protocol
           Version 1.3", RFC 9846, DOI 10.17487/RFC9846, July 2026,
           <https://www.rfc-editor.org/info/rfc9846>.

[TLS13REG] Salowey, J. and S. Turner, "IANA Registry Updates for TLS
           and DTLS", RFC 9847, DOI 10.17487/RFC9847, December 2025,
           <https://www.rfc-editor.org/info/rfc9847>.

5.2. Informative References

[CFRGSLIDES]
           McGrew, D., "Post Quantum Secure Cryptography Discussion",
           IETF 95 Proceedings, April 2016,
           <https://www.ietf.org/proceedings/95/slides/slides-95-
           cfrg-4.pdf>.

[ETSI]     ETSI, "CYBER; Migration strategies and recommendations to
           Quantum Safe schemes", Version 1.1.1, ETSI TR 103 619,
           July 2020, <https://www.etsi.org/deliver/
           etsi_tr/103600_103699/103619/01.01.01_60/
           tr_103619v010101p.pdf>.

[ML-DSA]   NIST, "Module-Lattice-Based Digital Signature Standard",
           NIST FIPS 204, DOI 10.6028/NIST.FIPS.204, August 2024,
           <https://csrc.nist.gov/pubs/fips/204/final>.

[ML-KEM]   NIST, "Module-Lattice-Based Key-Encapsulation Mechanism
           Standard", NIST FIPS 203, DOI 10.6028/NIST.FIPS.203,
           August 2024, <https://csrc.nist.gov/pubs/fips/203/final>.

[PQC]      NIST, "Post-Quantum Cryptography (PQC)", January 2017,
           <https://csrc.nist.gov/projects/post-quantum-
           cryptography>.

[PQUIPWG]  IETF, "Post-Quantum Use in Protocols",
           <https://datatracker.ietf.org/wg/pquip/about/>.

[SLH-DSA]  NIST, "Stateless Hash-Based Digital Signature Standard",
           NIST FIPS 205, DOI 10.6028/NIST.FIPS.205, August 2024,
           <https://csrc.nist.gov/pubs/fips/205/final>.

[TLSWG]    IETF, "Transport Layer Security",
           <https://datatracker.ietf.org/wg/tls/about/>.

Acknowledgments 🫶

We gratefully thank Amanda Baber, David Dong, and Sabrina Tanamal of IANA for helping revise and clarify Section 4 💖.

Authors' Addresses ✍️

Rich Salz Akamai Technologies Email: rsalz@akamai.com

Nimrod Aviram Email: nimrod.aviram@gmail.com

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