What is CVE-2016-5117?

CVE-2016-5117 is a medium-severity vulnerability in Openntpd, classified under CWE-254. CVSS score: 5.9/10. Published 2017-01-31.

How severe is CVE-2016-5117?

Medium severity. CVSS v3 base score is 5.9 out of 10.

Vulnerability in Openntpd

CVE-2016-5117

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.

Published 2017-01-31 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.007 (51.5th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Openntpd

Weakness classification (CWE)

CWE-254

References

cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/ntpd/constraint.c.diff (Patch)
www.openwall.com/lists/oss-security/2016/05/23/2 (mailing-list, Mailing List, Third Party Advisory)
www.openwall.com/lists/oss-security/2016/05/29/6 (mailing-list, Mailing List, Third Party Advisory)
www.openntpd.org/txt/release-6.0p1.txt (Vendor Advisory)

Frequently asked questions

What is CVE-2016-5117?: CVE-2016-5117 is a medium-severity vulnerability in Openntpd, classified under CWE-254. CVSS score: 5.9/10. Published 2017-01-31.
How severe is CVE-2016-5117?: Medium severity. CVSS v3 base score is 5.9 out of 10.