Update OpenSSL on Mac: LibreSSL 3.3.6 Failed 18 of 26 Probes

The openssl that comes with a Mac isn't OpenSSL. On this Mac mini, running macOS 26.4.1, /usr/bin/openssl version prints LibreSSL 3.3.6. That is OpenBSD's fork, and the LibreSSL release list dates 3.3.6 to March 15, 2022. The same page lists 4.3.3 as of October 4, 2026. Apple rebuilt the 1.1 MB binary for this OS release (it's dated April 6, 2026), but the version inside it didn't move.

This continues my run through the tools macOS bundles, after update Git on Mac, update Python on Mac, update Ruby on Mac and curl on Mac. OpenSSL turned out different from the others in two ways. Homebrew now has two current major versions, 3.6.5 and 4.0.3, and this morning one of them quietly took over my PATH. And the stock LibreSSL doesn't just lack features: for 5 of them it reports success.

26 probes against three openssl binaries

I wrote a 28-row probe script covering things people actually paste from answers and READMEs: Ed25519 and X25519 keys, ML-DSA and ML-KEM keys, req -noenc and -addext, x509 -ext and x509 -new, SHA-3 and BLAKE2 digests, the kdf, mac, list, engine and rehash commands, ChaCha20 in enc, and TLS 1.3 and post-quantum key exchange against cloudflare.com. I ran it on /usr/bin/openssl (LibreSSL 3.3.6), Homebrew's openssl@3 (3.6.5) and Homebrew's openssl@4 (4.0.3), each in a fresh temp directory. Two rows are controls that should fail everywhere (a made-up command and -ssl3), which leaves 26 features.

LibreSSL's 13 errors are the honest kind. genpkey -algorithm ed25519 prints Algorithm ed25519 not found, and the ML-DSA and ML-KEM requests fail the same way. x509 -ext and x509 -new say unknown option, and dgst -sha3-256, -blake2b512 and -sha512-256 print the usage text and exit 1. req -noenc, the OpenSSL 3 spelling of -nodes, also exits 1, so a certificate recipe written for OpenSSL 3 fails here unless it uses the old flag. LibreSSL's own ChangeLog puts Ed25519 and X25519 key support "via OpenSSL's EVP" in 3.7.0, a later release than the one Apple ships.

The 5 that exit 0

When the LibreSSL 3.3.6 binary doesn't know a subcommand, it prints an error and the full command list, and then exits 0:

$ /usr/bin/openssl kdf -keylen 32 -kdfopt digest:SHA256 -kdfopt key:secret HKDF
openssl:Error: 'kdf' is an invalid command.

Standard commands
asn1parse         ca                certhash          ciphers
...
$ echo $?
0

That happened for kdf, mac, list, engine and rehash, and for my control command openssl frobnicate. Both OpenSSL builds exit 1 with Invalid command 'frobnicate'. So a script that runs openssl rehash certs/ under set -e keeps going on a stock Mac with nothing hashed. LibreSSL calls that command certhash, which is the one probe both OpenSSL builds fail.

The TLS 1.3 row is the reverse problem. LibreSSL 3.3.6 does speak TLS 1.3: piped from echo, it negotiated TLSv1.3 with AEAD-CHACHA20-POLY1305-SHA256. But the usual health-check form, openssl s_client -connect host:443 </dev/null, exited 1 on 10 of 10 runs against cloudflare.com and github.com. The same handshake piped from echo exited 0 on 10 of 10, and OpenSSL 4.0.3 exited 0 with </dev/null on all 10. A certificate check that tests $? will mark a healthy host as down if it runs on Apple's binary.

Probe	LibreSSL 3.3.6	OpenSSL 3.6.5	OpenSSL 4.0.3
openssl kdf ... HKDF	error text, exit 0	works	works
openssl rehash dir	error text, exit 0	works	works
openssl engine	error text, exit 0	works	exit 1, removed
s_client default group, cloudflare.com	X25519	X25519MLKEM768	X25519MLKEM768
-groups X25519MLKEM768	Failed to set groups	works	works
genrsa output header	BEGIN RSA PRIVATE KEY	BEGIN PRIVATE KEY	BEGIN PRIVATE KEY
x509 -fingerprint -sha256 label	SHA256 Fingerprint=	sha256 Fingerprint=	sha256 Fingerprint=

Some things matched across all three. enc -aes-256-cbc files decrypted on every binary in both directions, with and without -pbkdf2, 18 of 18. genrsa defaults to 2048 bits everywhere, req -x509 without -days gives 30 days everywhere, and all three verified cloudflare.com's chain with Verify return code: 0 (ok), each from its own trust store (/private/etc/ssl for Apple, /opt/homebrew/etc/openssl@3 or @4 for Homebrew). The enc matrix also caught me: my first run reported 6 failures because I captured output with 2>&1, and OpenSSL's *** WARNING : deprecated key derivation used. line landed in the plaintext. The warning goes to stderr, so keep it there.

Which Homebrew openssl you get now

brew info openssl answers openssl@4: stable 4.0.3 with Aliases: openssl. openssl@3 is 3.6.5, and the OpenSSL project's release strategy page says 3.6 is supported until 2026-11-01, 20 days from today. 4.0 runs to 2027-05-14, and the long-term release is 3.5, supported until 2030-04-08, which Homebrew packages as the keg-only [email protected] (3.5.9).

On this Mac, 16 installed formulae depend on openssl@3 (curl, wget, node, tmux, ollama, Python 3.12 and 3.13 among them) and 6 depend on openssl@4, starting with [email protected]. Only one of the two can own /opt/homebrew/bin/openssl. At 07:33 this morning a brew install sigrok-cli pulled in openssl@4, which unlinked openssl@3, and the openssl on my PATH went from 3.6.5 to 4.0.3 with no prompt. I saw the same switch yesterday with Ruby, written up in update Ruby on Mac. If a script depends on a particular major version, call it by its keg path: /opt/homebrew/opt/openssl@3/bin/openssl or /opt/homebrew/opt/openssl@4/bin/openssl.

What 4.0 changes for a shell user

The OpenSSL 4.0 NEWS file lists removed engines, SSLv3, the SSLv2 Client Hello and the c_rehash script. Most of the list affects C code. For the command line, I hit three changes:

• openssl engine is gone: Invalid command 'engine', exit 1.
• -text output changed. For the same RSA key, 3.6.5 and LibreSSL print the modulus as 00:c9:82:e4:... and 4.0.3 prints c9:82:e4:.... Signature dumps went from 18 to 24 bytes per line. The md5 of rsa -noout -text differed between 3.6.5 and 4.0.3, so anything that diffs or greps that text will break.
• -modulus didn't change. The usual key-matches-certificate check (x509 -noout -modulus | md5 against rsa -noout -modulus | md5) gave the same hash, bc1c2d6d..., on all three binaries.

In the Hacker News thread on the 4.0.0 release, one commenter wrote that compared to OpenSSL 3 "this transition has been very smooth" and only the engine removal caused trouble in Fedora. Another said they had benchmarked an average 10% slowdown. I didn't see that on the M4. With openssl speed -seconds 2, 4.0.3 against 3.6.5 did AES-256-GCM at 9.87 to 9.92 GB/s against 10.07 to 10.09, SHA-256 at 3.36 GB/s on both, ECDSA P-256 signing at 96,823/s against 97,723/s, and RSA-2048 signing at 3,136 to 3,149/s against 3,147 to 3,186/s. That's at most 2% in four primitives, not 10%. I didn't test TLS handshakes or QUIC.

How I'd update it

brew install openssl@4        # or [email protected] for the LTS (keg-only)
type -a openssl              # /opt/homebrew/bin/openssl should be listed first
openssl version              # OpenSSL 4.0.3 29 Sep 2026
/usr/bin/openssl version     # still LibreSSL 3.3.6

Leave /usr/bin/openssl alone. It's on the signed system volume, so you can't replace it anyway. For scripts that run under launchd, whose default PATH is /usr/bin:/bin:/usr/sbin:/sbin, write the full keg path, because a bare openssl there gets LibreSSL and its exit-0 errors. If a recipe only needs RSA or ECDSA keys, a PKCS#12 bundle or a quick s_client, LibreSSL can still do it. The exceptions are the PKCS#12 MAC traps in Mac verify error: invalid password and anything involving Ed25519, SHA-3 or ML-KEM.

FAQ

How do I update OpenSSL on my Mac?

Install it with Homebrew: brew install openssl@4 gives you OpenSSL 4.0.3, and brew install [email protected] gives you the long-term-support 3.5 line, which is keg-only. Make sure /opt/homebrew/bin comes before /usr/bin in your PATH, then check with type -a openssl and openssl version. Don't try to replace /usr/bin/openssl. It's Apple's LibreSSL 3.3.6 on the read-only system volume and stays there.

Why does openssl version still say LibreSSL?

macOS ships LibreSSL 3.3.6 as /usr/bin/openssl, and Homebrew installs OpenSSL to /opt/homebrew/bin (or /usr/local/bin on Intel Macs) without touching it. If /usr/bin comes first in your PATH, or a cron or launchd job runs with the default PATH, you get LibreSSL. If you have both openssl@3 and openssl@4 installed, Homebrew links only one of them, and installing a package that depends on the other can switch which one the bare openssl command runs.

Should I install OpenSSL 3 or OpenSSL 4 on a Mac?

For command-line use, either works for nearly everything: 3.6.5 passed 25 of 26 probes and 4.0.3 passed 24, with the engine command as the extra loss. Homebrew's openssl@3 is 3.6, and the OpenSSL project supports 3.6 only until November 1, 2026, so if you want the 3.x line long term, use [email protected] (supported to April 2030). 4.0 is supported to May 2027 and is what brew install openssl now installs.

Method: on October 12, 2026 I ran the same probe script (probe.sh, 28 rows including 2 controls) on a Mac mini M4 (Mac16,10) running macOS 26.4.1 (25E253) against /usr/bin/openssl (LibreSSL 3.3.6), Homebrew openssl@3 3.6.5 and openssl@4 4.0.3, each by full keg path in a fresh /tmp directory. A probe counts as worked when the command exited 0 and, where it applies, the output had the expected content (for example, the SAN in the certificate made with -addext). Network rows connected to cloudflare.com, and the stdin test used cloudflare.com and github.com 5 times each. Speed figures are single 2-second openssl speed runs, two runs for AES and SHA-256, on an otherwise idle machine. The LibreSSL dates come from libressl.org's release list and the libressl/portable ChangeLog, the support dates from openssl-library.org, and the 4.0 changes from its NEWS.md. I didn't test Intel Macs, MacPorts, LibreSSL 4.x, or anything that links the libraries from C or Python. The script and per-binary results are in research/update-openssl-mac-raw. I left Homebrew's link state as I found it, with openssl@4 linked.