Subject: [ASA-201810-10] libssh: authentication bypass

Arch Linux Security Advisory ASA-201810-10
==========================================

Severity: Critical
Date    : 2018-10-17
CVE-ID  : CVE-2018-10933
Package : libssh
Type    : authentication bypass
Remote  : Yes
Link    : https://security.archlinux.org/AVG-780

Summary
=======

The package libssh before version 0.8.4-1 is vulnerable to
authentication bypass.

Resolution
==========

Upgrade to 0.8.4-1.

# pacman -Syu "libssh>=0.8.4-1"

The problem has been fixed upstream in version 0.8.4.

Workaround
==========

None.

Description
===========

An authentication bypass vulnerability has been discovered in libssh
versions prior to 0.7.6 and 0.8.4, in the server-side state machine. By
presenting the server an SSH2_MSG_USERAUTH_SUCCESS message in place of
the SSH2_MSG_USERAUTH_REQUEST message which the server would expect to
initiate authentication, the attacker could successfully authenticate
without any credentials, resulting in unauthorized access.

Impact
======

A remote attacker is able to successfully authenticate without any
credentials, resulting in unauthorized access.

References
==========

https://www.libssh.org/2018/10/16/libssh-0-8-4-and-0-7-6-security-and-bugfix-release/
https://www.libssh.org/security/advisories/CVE-2018-10933.txt
https://git.libssh.org/projects/libssh.git/commit/?id=2bddafeb709eacc80ad31fec40479f9b628a8bd7
https://git.libssh.org/projects/libssh.git/commit/?id=825f4ba96407abe8cebb046a7503fa2bf5de9df6
https://git.libssh.org/projects/libssh.git/commit/?id=20981bf2296202e95d7919394d4610ae3a876cfa
https://git.libssh.org/projects/libssh.git/commit/?id=5d7414467d6dac100a93df761b06de5cd07fc69a
https://git.libssh.org/projects/libssh.git/commit/?id=459868c4a57d2d11cf7835655a8d1a5cf034ccb4
https://git.libssh.org/projects/libssh.git/commit/?id=68b0c7a93448123cc0d6a04d3df40d92a3fd0a67
https://git.libssh.org/projects/libssh.git/commit/?id=75be012b4a14f4550ce6ad3f126e559f44dbde76
https://git.libssh.org/projects/libssh.git/commit/?id=e1548a71bdac73da084174ab1d6d2713edd93f6e
https://security.archlinux.org/CVE-2018-10933