TLS 1.2 feature freeze: TLS 1.2 is in Feature Freeze
No more changes to TLS 1.2 beyond urgent security fixes, so new work, including post-quantum, goes to TLS 1.3.
Salz, R. and N. Aviram, "TLS 1.2 is in Feature Freeze", RFC 9851, DOI 10.17487/RFC9851, July 2026, <https://www.rfc-editor.org/info/rfc9851>.
@misc{rfc9851,
series = {Request for Comments},
number = 9851,
howpublished = {RFC 9851},
publisher = {RFC Editor},
doi = {10.17487/RFC9851},
url = {https://www.rfc-editor.org/info/rfc9851},
author = {R. Salz and N. Aviram},
title = {{TLS 1.2 is in Feature Freeze}},
pagetotal = 5,
year = 2026,
month = jul,
} RFC text
Contents
Internet Engineering Task Force (IETF) R. Salz
Request for Comments: 9851 Akamai Technologies
Category: Standards Track N. Aviram
ISSN: 2070-1721 July 2026
TLS 1.2 is in Feature Freeze
Abstract
Use of TLS 1.3, which fixes some known deficiencies in TLS 1.2, is
growing. This document specifies that no changes will be approved
for TLS 1.2 outside of urgent security fixes (as determined by TLS
Working Group consensus), new TLS Exporter Labels, and new
Application-Layer Protocol Negotiation (ALPN) Protocol IDs. This
applies to TLS only; it does not apply to DTLS (in 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
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9851.
Copyright Notice
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) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Revised BSD License text as described in Section 4.e of the
Trust Legal Provisions and are provided 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 known deficiencies with TLS 1.2 [TLS12]
and its use is growing. Some examples of the fixes include
encrypting more of the traffic so that it is not readable by
outsiders and removing most cryptographic primitives that are now
considered weak. Importantly, TLS 1.3 enjoys robust security proofs.
Both versions have several extension points. Items like new
cryptographic algorithms, new supported groups (formerly "named
curves"), etc., can be added without defining a new protocol. This
document specifies that no changes will be approved for TLS 1.2
outside of 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 DTLS, in any
DTLS version.
2. Implications for Post-Quantum Cryptography (PQC)
Cryptographically relevant quantum computers, once available, are
likely to greatly lessen the time and effort needed to break RSA,
finite-field-based Diffie-Hellman (FFDH), or Elliptic Curve
Cryptography (ECC) which are currently used in TLS. In 2016, the US
National Institute of Standards and Technology (NIST) started a
multi-year effort to standardize algorithms that will be "safe" once
quantum computers are feasible [PQC]. Initial discussions in the
IETF community happened around the same time [CFRGSLIDES].
In 2024, NIST released standards for [ML-KEM], [ML-DSA], and
[SLH-DSA]. Many other countries and organizations are publishing
their roadmaps, including the multi-national standards organization
ETSI [ETSI].
While the industry was waiting for NIST to finish standardization,
the IETF has had several efforts underway. A working group was
formed in early 2023 to work on the use of Post-Quantum Cryptography
(PQC) in IETF protocols [PQUIPWG]. Several other working groups,
including TLS [TLSWG], are working on specifications to support
hybrid algorithms and identifiers, for use during a 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. Put bluntly, PQC for TLS
1.2 will not be specified (see Section 4) at any time; anyone wishing
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 as an additional reason to upgrade to TLS 1.3.
4. IANA Considerations
No TLS registries [TLS13REG] are being closed by this document.
Rather, this document modifies the instructions to IANA and the TLS
Designated Experts to constrain the type of entries that can be added
to existing registries.
This document does not introduce any new limitations on the
registrations for either of 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 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 the following
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 document is approved for
publication should indicate whether the actions defined here are
applicable.
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 acknowledge Amanda Baber, David Dong, and Sabrina
Tanamal of IANA for their help in revising and clarifying Section 4.
Authors' Addresses
Rich Salz
Akamai Technologies
Email: rsalz@akamai.com
Nimrod Aviram
Email: nimrod.aviram@gmail.com
AI ELI5
On this page
§1The Freeze
TLS 1.3 fixes most known deficiencies of TLS 1.2. The RFC gives as examples that it encrypts more of the traffic so outsiders cannot read it, and removes most cryptographic primitives now considered weak. It also enjoys robust security proofs.
Both versions have extension points, so items such as new cryptographic algorithms and new supported groups can be added without defining a new protocol. This document specifies that no changes will be approved for TLS 1.2 outside urgent security fixes (as decided by TLS Working Group consensus) and the registry exceptions below. It applies to TLS only, not to DTLS in any version.
The old version still works, but the builders will only fix emergencies on it. All the new features go into the newer version.
§2Why Post-Quantum Cryptography Matters Here
The RFC explains that cryptographically relevant quantum computers, once available, are likely to greatly lessen the time and effort needed to break RSA, finite-field Diffie-Hellman and elliptic curve cryptography, which TLS uses today. NIST began a multi-year effort in 2016 to standardize algorithms that will be safe afterwards, and in 2024 released standards for ML-KEM, ML-DSA and SLH-DSA.
Several IETF working groups, including TLS, are working on hybrid algorithms and identifiers for the transition. The TLS Working Group's effort is focused exclusively on TLS 1.3 or later. In the RFC's blunt words, post-quantum cryptography for TLS 1.2 will not be specified at any time.
One day, super-powerful computers might crack today's secret codes. The new codes are being built only for the newer version, so you need to move to it to get them.
§4What Still Changes: Registry Rules
No TLS registries are closed. Instead the instructions to IANA and the TLS Designated Experts are modified to limit what can be added. There are no new limits on two registries: TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs and TLS Exporter Labels.
The other TLS registries get a note saying that any 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 carry an informal indication like "For TLS 1.3 or later", for example in the Comment column. The note was added to registries including TLS Cipher Suites, TLS ExtensionType Values, TLS Supported Groups and TLS SignatureScheme.
The big list of allowed things gets a sticker: anything new is for the newer version only. Two small lists stay open as before.
§3Security Considerations
The whole document is about security. The RFC offers post-quantum security concerns as an additional reason to upgrade to TLS 1.3.
The reason for the whole rule is staying safe, and moving to the newer version is the safe choice.