CVE-2015-5600

Severity: high (CVSS 8.5 v2.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 9.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2015-08-03 · updated 2026-06-17
Weakness: CWE-264

Description

The kbdint_next_device function in auth2-chall.c in sshd in OpenSSH through 6.9 does not properly restrict the processing of keyboard-interactive devices within a single connection, which makes it easier for remote attackers to conduct brute-force attacks or cause a denial of service (CPU consumption) via a long and duplicative list in the ssh -oKbdInteractiveDevices option, as demonstrated by a modified client that provides a different password for each pam element on this list.

Affected products

OpenSSH: through 6.9

References

http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/auth2-chall.c
http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/auth2-chall.c.diff?r1=1.42&r2=1.43&f=h
http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10697
http://lists.apple.com/archives/security-announce/2015/Aug/msg00001.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-August/165170.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-July/162955.html
http://lists.opensuse.org/opensuse-security-announce/2015-09/msg00017.html
http://openwall.com/lists/oss-security/2015/07/23/4
http://rhn.redhat.com/errata/RHSA-2016-0466.html
http://seclists.org/fulldisclosure/2015/Jul/92
http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html
http://www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html

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