cbcvebase.
CVE-2016-6515
published 2016-08-07

CVE-2016-6515: The auth_password function in auth-passwd.c in sshd in OpenSSH before 7.3 does not limit password lengths for password authentication, which allows remote…

PriorityP264high7.5CVSS 3.0
AVNACLPRNUINSUCNINAH
EXPLOIT
EPSS
58.57%
99.0th percentile
The auth_password function in auth-passwd.c in sshd in OpenSSH before 7.3 does not limit password lengths for password authentication, which allows remote attackers to cause a denial of service (crypt CPU consumption) via a long string.

Affected

10 ranges
VendorProductVersion rangeFixed in
debianopenssh< openssh 1:7.3p1-1 (bookworm)openssh 1:7.3p1-1 (bookworm)
fedoraprojectfedora
openbsdopenssh<= 7.2
openbsdopenssh>= 0 < 1:7.3p1-11:7.3p1-1
openbsdopenssh>= 0 < 1:7.3p1-11:7.3p1-1
openbsdopenssh>= 0 < 1:7.3p1-11:7.3p1-1
openbsdopenssh>= 0 < 1:7.3p1-11:7.3p1-1
openbsdopenssh>= 0 < 1:6.6p1-2ubuntu2.81:6.6p1-2ubuntu2.8
openbsdopenssh>= 0 < 1:7.2p2-4ubuntu2.11:7.2p2-4ubuntu2.1
paloaltopan-os

Detection & IOCsextracted from sources · hover to see the quote

commandssh.connect(remote_ip, username='root', password=crafted_passwd)
  • Monitor sshd for sustained high CPU consumption correlated with incoming SSH password authentication attempts — the DoS manifests as crypt CPU consumption.
  • Alert on rapid, repeated SSH connection attempts in an infinite loop from a single source IP, consistent with the exploit's loop-based DoS pattern.
  • ·The vulnerability is only exploitable when PasswordAuthentication is enabled in sshd_config; disabling it fully mitigates the attack. On FreeBSD, PasswordAuthentication is disabled by default.
  • ·On Red Hat Enterprise Linux 6, 7, and 8, the impact of this vulnerability is mitigated by SELinux.

CVSS provenance

nvdv3.07.5HIGHCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvdv2.07.8HIGHAV:N/AC:L/Au:N/C:N/I:N/A:C
osv7.5HIGH
vendor_debian7.5HIGH
vendor_redhat7.5HIGH
vendor_ubuntu5.9MEDIUM
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