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Message-ID: <44a148df1151d38d@cvs.openbsd.org>
Date: Mon, 6 Jul 2026 03:28:35 -0600 (MDT)
From: Damien Miller <djm@....openbsd.org>
To: oss-security@...ts.openwall.com
Subject: Announce: OpenSSH 10.4 released
OpenSSH 10.4 has just been released. It will be available from the
mirrors listed at https://www.openssh.com/ shortly.
OpenSSH is a 100% complete SSH protocol 2.0 implementation and
includes sftp client and server support.
Once again, we would like to thank the OpenSSH community for their
continued support of the project, especially those who contributed
code or patches, reported bugs, tested snapshots or donated to the
project. More information on donations may be found at:
https://www.openssh.com/donations.html
Potentially-incompatible changes
--------------------------------
* sshd(8): configuration dump mode ("sshd -G") now writes directives
in mixed case (e.g. "PubkeyAuthentication") whereas previously it
emitted only lower-case names.
* sshd(8): on Linux systems with the seccomp sandbox enabled,
failures to enable SECCOMP or NO_NEW_PRIVS are now fatal.
Previously sshd(8) would log the error but continue operation,
to support systems that lacked these features. Now systems that
lack these should instead disable the sandbox at configure time.
* ssh(1), sshd(8): make the transport protocol stricter by
disconnecting if the peer sends non-KEX messages during a post-
authentication key re-exchange. Previously a malicious peer could
continue sending non-key exchange messages without penalty. These
would be buffered, causing memory to be wasted up until the
connection terminated or the server/client hit a memory limit.
Implementations that do not restrict messages sent during key
exchange as per RFC4253 section 7.1 may be disconnected.
Reported by Marko Jevtic.
Changes since OpenSSH 10.3
==========================
This release contains a number of security fixes as well as general
bugfixes and a couple of new features.
Security
========
* sftp(1): when downloading files on the command-line using
"sftp host:/path .", a malicious server could cause the file to
be downloaded to an unexpected location. This issue was identified
by the Swival Security Scanner.
* scp(1): when copying files between two remote destinations, do
not allow a malicious server to write files to the parent
directory of the intended target directory. This issue was
identified by the Swival Security Scanner.
* sshd(8): when using the "internal-sftp" SFTP server implementation
(this is not the default), long command lines were previously
truncated silently after the 9th argument. If a security-relevant
option was in the 10th or later position, it would be discarded.
Reported by Steve Caffrey.
* sshd(8): add a documentation note to mention that the
GSSAPIStrictAcceptorCheck option is ineffective when the server
is joined to a Windows Active Directory. Reported by Yarin Aharoni
of Safebreach.
* sshd(8): DisableForwarding=yes didn't override PermitTunnel=yes
as it was documented to do. Note that PermitTunnel is not enabled
by default. Reported independently by Huzaifa Sidhpurwala of
Redhat and Marko Jevtic.
* sshd(8): avoid a potential pre-authentication denial of service
when GSSAPIAuthentication was enabled (this feature is off by
default). This was not mitigated by MaxAuthTries, but would be
penalised by PerSourcePenalties. This was reported by Manfred
Kaiser of the milCERT AT (Austrian Ministry of Defence).
* sshd(8): fix a number of cases where the minimum authentication
delay was not being enforced. Reported by the Orange Cyberdefense
Vulnerability Team.
* ssh(1): fix a possible client-side use-after-free if the server
changes its host key during a key reexchange. This was reported by
Zhenpeng (Leo) Lin of Depthfirst.
New features
------------
* All: add experimental support for a composite post-quantum
signature scheme that combines ML-DSA 44 and Ed25519 as specified
in draft-miller-sshm-mldsa44-ed25519-composite-sigs.
This scheme is not enabled by default. To use it, you'll need
to add it to HostKeyAlgorithms, PubkeyAcceptedAlgorithms, etc.
Keys may be generated using "ssh-keygen -t mldsa44-ed25519".
* ssh(1), sshd(8): replace the wildcard pattern matcher with an
implementation based on an NFA. This avoids exponential worst-case
behaviour for the old implementation.
Bugfixes
--------
* ssh-agent(1): fix incorrect reply to "query" SSH_AGENTC_EXTENSION
requests. bz3967
* sshd(8): avoid sending observably different messages for valid vs
invalid users in GSSAPIAuthentication (disabled by default).
* ssh(1), sshd(8): fix several bugs that incorrectly
classified bulk traffic as interactive. bz3972, bz3958
* ssh-keygen(1), ssh-add(1): skip unsupported key types when
downloading resident keys from a FIDO token. Previously, downloads
would abort when one was encountered. GHPR657
* ssh(1): fix a potential use-after-free on an error path if
cipher_init() fails.
* sshd(8): perform stricter encoding and validation of transport
state passed between sshd privilege separation subprocesses. This
somewhat further hardens the server against attacks on sshd-auth
or sshd-session subprocesses.
* ssh-agent(1): avoid possible runtime denial of service by
enforcing some limits on the length of usernames in key use
constraints.
* sftp(1): fix two separate one-byte out-of-bounds reads, in
SSH2_FXP_REALPATH and batch command processing.
* sftp-server(8): disallow use of the copy-data extension to read
and write to the same inode simultaneously.
* ssh(1), sshd(8): avoid strlen(NULL) crash if an X11 channel was
created before the x11-req SSH_MSG_CHANNEL_REQUEST was sent.
GHPR679
* sftp(1), scp(1): avoid a situation where sftp_download() could get
stuck in a loop if a broken server repeatedly returned zero length
while reading a file.
* ssh(1): avoid leaking DNS0x20 case-randomised names into names
canonicalised using CanonicalizePermittedCNAMEs. bz3966
* sftp-server(8): avoid truncation of pathnames passed to lstat()
during SSH_FXP_REALPATH handling on systems where PATH_MAX is not
the actual max. GHPR688
* ssh(1), sshd(8): correct arming of poll(2) event masks for some
socket-type channels. GHPR660
* sshd(8): major refactor of sshd_config parsing and management
code, to allow for more exact serialisation/deserialisation across
privilege separation boundaries.
* ssh-add(1): open connection to the agent only after getopt()
processing has completed, to give options like "-v" a chance to
display debug information about this operation.
* crypto code: fix bounds checking when signing messages of length
greater than will fit in a size_t. In OpenSSH, message sizes are
bounded by SSHBUF_SIZE_MAX so this was unreachable.
* crypto code: add signature malleability and pubkey validity checks
to ed25519 verification. SSH doesn't depend on these properties
* crypto code: fix ECDSA order check for curves with cofactor != 1.
All supported EC curves have cofactor 1, so this was
unreachable.
* sshd(8): differentiate between execution failures and a subsystem
that was not found when logging why a subsystem failed to start.
GHPR637
* All: use safer idioms for timegm(3) and mktime(3) error detection.
* ssh(1), sshd(8): avoid accepting invalid cipher or MAC lists in
config files or command-line arguments. This could cause runtime
failures later.
* ssh(1): fix NULL deref crash during pubkey auth when using a PEM
style private key with no corresponding .pub key adjacent to it.
* sshd(8): don't print an error message when trying to load a host
private key when PKCS#11 keys are in use, as these don't need the
private half on the filesystem. GHPR664
* All: don't use deprecated ERR_load_crypto_strings(). GHPR650
* ssh(1): properly report errors during configuration default
setting. GHPR649
* ssh(1): use correct directive name (Match instead of Host) in
error message. bz3968
* sftp(1): fix "ls -ln" which was not correctly showing numeric
UID/GIDs but rather user and group names. bz3953
* sshd(8): avoid possible NULL dereference if an allocation fails
during config parsing. bz3948
* All: fix ineffective guards against loading overly large public
keys in several places. bz3969 and bz3970
* sftp(1): ensure file descriptors used by sftp to communicate to
its ssh(1) subprocess don't leak into executed subprocesses (e.g.
via "!"). GHPR693
Portability
-----------
* Sync fmt_scaled.c with OpenBSD upstream, picking up an exactness
fix for large exponents (GHPR671)
* sshd(8): remove duplicate sandbox entry for clock_gettime64.
* ssh(1), sshd(8): use correct IPTOS_DSCP_VA value if not provided
by the system headers.
* Sync getrrsetbyname.c with OpenBSD upstream, picking up robustness
fixes.
* Disable replacements in openbsd-compat for strvisx(3) and
stravis(3), as these are unused in OpenSSH
* Avoid fortify warnings on Android bz3954
* Fix a number of memory leaks on error paths in the portability
code. GHPR681
* Revise the README.privsep documentation to reflect sshd's recent
switch to a multi-binary model.
Checksums:
==========
- SHA1 (openssh-10.4.tar.gz) = 8502b516230865e229d55045bb4ccc67aeae905b
- SHA256 (openssh-10.4.tar.gz) = qUVI+wMg4mVpiQbXvfMVkF3Zuyy2JrS+ZjN764mtyGE=
- SHA1 (openssh-10.4p1.tar.gz) = ae8650a71cc52dbbd049519cee276ae6d65c2c4d
- SHA256 (openssh-10.4p1.tar.gz) = 72Am3SrqjVYFljjV0yYpAsiSzrqfiDlYNeDQbT+2Mjg=
Please note that the SHA256 signatures are base64 encoded and not
hexadecimal (which is the default for most checksum tools). The PGP
key used to sign the releases is available from the mirror sites:
https://cdn.openbsd.org/pub/OpenBSD/OpenSSH/RELEASE_KEY.asc
Reporting Bugs:
===============
- Please read https://www.openssh.com/report.html
Security bugs should be reported directly to openssh@...nssh.com
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