CVE-2016-5117

Severity: medium (CVSS 5.9 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2017-01-31 · updated 2026-06-17
Weakness: CWE-254

Description

OpenNTPD before 6.0p1 does not validate the CN for HTTPS constraint requests, which allows remote attackers to bypass the man-in-the-middle mitigations via a crafted timestamp constraint with a valid certificate.

Affected products

Openntpd: through 6.0

References

http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/ntpd/constraint.c.diff?r1=1.27&r2=1.28
http://www.openntpd.org/txt/release-6.0p1.txt
http://www.openwall.com/lists/oss-security/2016/05/23/2
http://www.openwall.com/lists/oss-security/2016/05/29/6
http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/ntpd/constraint.c.diff?r1=1.27&r2=1.28
http://www.openntpd.org/txt/release-6.0p1.txt
http://www.openwall.com/lists/oss-security/2016/05/23/2
http://www.openwall.com/lists/oss-security/2016/05/29/6

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