# OpenSSL 4.1.0

> Source: <https://github.com/openssl/openssl/releases/tag/openssl-4.1.0>
> Published: 2026-10-23 12:42:44+00:00

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[openssl-machine](https://github.com/openssl-machine)released this

[438 commits](https://github.com/openssl/openssl/compare/openssl-4.1.0...master)to master since this release

OpenSSL 4.1.0 is a feature release adding significant new functionality

to OpenSSL.

This release incorporates the following potentially significant or incompatible

changes:

- 
Added `VC-WIN32-MSVC2013` and`VC-WIN64A-MSVC2013` build targets to provide
 internal functions for bridging the gaps in C99 standard support
that are present in MSVC 2013.
- 
Added optimized ML-DSA and ML-KEM NTT operations on `ppc64le` ;
 optimized ML-DSA operations on`x86_64` ;
 AVX-512-optimized SHAKE x4 operations for ML-DSA on`x86_64` ;
 AVX-512 and VAES optimizations for AES-CBC decryption on`x86_64` .
- 
Changed `tsget` utility to use`Net::Curl::Easy` (from the`Net-Curl` CPAN
 distribution) instead of the abandoned`WWW::Curl::Easy` .  Users who rely
 on`tsget` should install`Net::Curl::Easy` before upgrading.
- 
Dropped Windows-on-Itanium ( `VC-WIN64I` ) and Windows CE (`VC-CE` ) targets
from Configurations.
- 
Dropped `no-ecdsa` and`no-ecdh` options from`Configure` , as these options
 did not really disable the implementations. Use`no-ec` to disable
the elliptic curve support.

This release adds the following new features:

- 
Support for DTLS 1.3 ( [RFC 9147](https://datatracker.ietf.org/doc/html/rfc9147) ).
 Refer to the`ossl-guide-dtlsv13(7)` manual page for details.
- 
Support for [RFC 8701](https://datatracker.ietf.org/doc/html/rfc8701) GREASE (Generate Random Extensions And Sustain
Extensibility).
- 
DTLS support in the SSL listener API.
- 
Support for IKEV2 KDF.
- 
Initial support for the Elbrus2000 ( `e2k` ) architecture.

Known issues in 4.1.0:

- 
[#32878](https://github.com/openssl/openssl/issues/32878)
 When a DTLS 1.3 KeyUpdate is received, all other outstanding
 post-handshake records are dropped from the retransmission buffer.
 This means post-handshake records still awaiting an ACK (such as a
 NewSessionTicket) will no longer be retransmitted if the original
 transmission is lost. A fix is in progress and planned for a future
release.
- 
[#33277](https://github.com/openssl/openssl/issues/33277)
 A permanent receive failure on a DTLS listener can be reported as
 `SSL_ERROR_WANT_READ` on an accepted connection. Polling and subsequent
 accept calls may also fail to report the error, causing applications
to continue waiting after a permanent failure.
- 
[#33278](https://github.com/openssl/openssl/issues/33278)
 A retryable write failure on a nonblocking connection accepted from a
 DTLS listener can be reported as`SSL_ERROR_SYSCALL` instead of
 `SSL_ERROR_WANT_WRITE` . Applications treating this result as fatal may
close a connection that is still usable.
- 
[#33242](https://github.com/openssl/openssl/issues/33242)
 DTLS 1.3 servers may abort handshakes with an`unexpected_message` alert
 when a client acknowledges part or all of the server's first flight
 before sending its response. This can occur after packet loss or while
the client is preparing its authentication response.