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CVE-2016-1550

21
FAUCET Score

CVE-2016-1550 is an exploitable vulnerability in the message authentication functionality of libntp, affecting ntp 4.2.8p4 and NTPSec a5fb34b9cc89b92a8fef2f459004865c93bb7f92. An unauthenticated attacker can send crafted messages to attempt to recover the message digest key. Rated Medium severity (CVSS 5.3), this vulnerability has a low potential impact of disclosing sensitive information with low attack complexity. There is no evidence of active exploitation, nor is public exploit code available, though it has received some community discussion and media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
4.2.8CPE matchmatch criteria
cpe:2.3:a:ntp:ntp:4.2.8:p4:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

5.3MEDIUM

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.0

Exploit Intelligence

EPSS Score
3.63%
Probability of exploitation in next 30 days
EPSS Percentile
88.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0363 is in the 85th percentile among its peer group of 23,705 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: ntp-0:4.2.6p5-10.el6.1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6.7 Extended Update SupportFixed in: ntp-0:4.2.6p5-5.el6_7.5
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: ntp-0:4.2.6p5-22.el7_2.2
View patch
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: ntp

Vendor Advisories (1)

redhatCVE-2016-1550Low

ntp: libntp message digest disclosure

Apr 26, 2016

References

lists.fedoraproject.org / pipermail/package-announce/2016-May/183647.html
lists.fedoraproject.org / pipermail/package-announce/2016-May/184669.html
lists.opensuse.org / opensuse-security-announce/2016-05/msg00034.html
lists.opensuse.org / opensuse-security-announce/2016-05/msg00037.html
lists.opensuse.org / opensuse-security-announce/2016-05/msg00052.html
lists.opensuse.org / opensuse-security-announce/2016-06/msg00001.html
lists.opensuse.org / opensuse-security-announce/2016-06/msg00020.html
lists.opensuse.org / opensuse-security-announce/2016-07/msg00026.html
lists.opensuse.org / opensuse-security-announce/2016-08/msg00042.html
lists.opensuse.org / opensuse-updates/2016-05/msg00114.html
packetstormsecurity.com / files/136864/Slackware-Security-Advisory-ntp-Updates.html
rhn.redhat.com / errata/RHSA-2016-1552.html
access.redhat.com / errata/RHSA-2016:1141
cert-portal.siemens.com / productcert/pdf/ssa-211752.pdf
cert-portal.siemens.com / productcert/pdf/ssa-497656.pdf
security.freebsd.org / advisories/FreeBSD-SA-16:16.ntp.asc
security.gentoo.org / glsa/201607-15
security.netapp.com / advisory/ntap-20171004-0002
us-cert.cisa.gov / ics/advisories/icsa-21-103-11
us-cert.cisa.gov / ics/advisories/icsa-21-159-11
arista.com / en/support/advisories-notices/security-advisories/1332-security-advisory-19
debian.org / security/2016/dsa-3629
kb.cert.org / vuls/id/718152
talosintelligence.com / vulnerability_reports/TALOS-2016-0084
tools.cisco.com / security/center/content/CiscoSecurityAdvisory/cisco-sa-20160428-ntpd
debian.org / security/2016/dsa-3629
oracle.com / technetwork/topics/security/bulletinapr2016-2952098.html
oracle.com / technetwork/topics/security/linuxbulletinapr2016-2952096.html
securityfocus.com / archive/1/538233/100/0/threaded
securityfocus.com / archive/1/archive/1/538233/100/0/threaded
securityfocus.com / bid/88261
securitytracker.com / id/1035705
talosintelligence.com / reports/TALOS-2016-0084
Technical DescriptionThird Party Advisory
ubuntu.com / usn/USN-3096-1