The monitor component in sshd in OpenSSH before 7.0 on non-OpenBSD platforms accepts extraneous username data in MONITOR_REQ_PAM_INIT_CTX requests, which allows local users to conduct impersonation attacks by leveraging any SSH login access in conjunction with control of the sshd uid to send a crafted MONITOR_REQ_PWNAM request, related to monitor.c and monitor_wrap.c.

References

• https://nvd.nist.gov/vuln/detail/CVE-2015-6563
• openssh/openssh-portable@d4697fe
• https://lists.debian.org/debian-lts-announce/2018/09/msg00010.html
• https://security.gentoo.org/glsa/201512-04
• https://support.apple.com/HT205375
• https://www.broadcom.com/support/fibre-channel-networking/security-advisories/brocade-security-advisory-2019-766
• http://lists.apple.com/archives/security-announce/2015/Oct/msg00005.html
• http://lists.fedoraproject.org/pipermail/package-announce/2015-August/165170.html
• http://lists.opensuse.org/opensuse-security-announce/2015-09/msg00017.html
• http://rhn.redhat.com/errata/RHSA-2016-0741.html
• http://seclists.org/fulldisclosure/2015/Aug/54
• http://www.openssh.com/txt/release-7.0
• http://www.openwall.com/lists/oss-security/2015/08/22/1
• http://www.oracle.com/technetwork/topics/security/bulletinjan2016-2867206.html
• http://www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
• http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2015-2719645.html
• http://www.securityfocus.com/bid/76317
• https://cert-portal.siemens.com/productcert/pdf/ssa-412672.pdf
• https://security.netapp.com/advisory/ntap-20180201-0002