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Fencer Intel
critical 9.8

CVE-2015-7871 in the critical feed json

Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass authentication.

published 2017-08-07 9 y ago modified 2026-06-17 4 mo ago also EUVD-2015-7769

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
81.8%
EPSS 81.8% chance of exploitation in 30 days, percentile 99.6%
public exploits
1
Metasploit

Summary

Crypto-NAK packets in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to bypass authentication.

Patch / fix

  • ntp ntp 4.2.8, 4.3.77
  • ntp Debian 11 1:4.2.8p4+dfsg-1

debian advisories DEBIAN-CVE-2015-7871

  • ntp Ubuntu 14.04 LTS 1:4.2.6.p5+dfsg-3ubuntu2.14.04.5

ubuntu advisories UBUNTU-CVE-2015-7871

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • ntp SLES 11 SP3-TERADATA, SLES 11 SP3-LTSS, SLES 11 SP2-LTSS +3 more 4.2.8p6-41.1
  • ntp SLES for SAP 12, SLES 12, SLED 12 4.2.8p6-46.5.2
  • yast2-ntp-client SLES for SAP 12, SLES 12, SLED 12 +1 more 3.1.12.4-8.2
  • ntp SLES for SAP 11 SP4, SLES 11 SP4, SLED 11 SP4 4.2.8p4-5.1
  • yast2-ntp-client SLES 11 SP2-LTSS 2.17.14.1-1.12.1

suse advisories SUSE-SU-2016:1311-1SUSE-SU-2016:1247-1SUSE-SU-2015:2058-1

  • ntp openSUSE Tumbleweed 4.2.8p9-1.1

opensuse advisories openSUSE-SU-2024:10181-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2015-7871 updated cvss 6.4

ntp: crypto-NAK symmetric association authentication bypass vulnerability

  • Red Hat Enterprise Linux 5 ntp Red Hat Enterprise Linux 6 ntp, ntpdate, ntp-perl Red Hat Enterprise Linux 7 ntp, sntp, ntpdate, ntp-perl
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-21-103-11 updated cvss 9.8

Siemens TIM 4R-IE Devices

  • Siemens SIPLUS NET TIM 4R-IE (6AG1800-4BA00-7AA0) Siemens SIPLUS NET TIM 4R-IE DNP3 (6AG1803-4BA00-7AA0) Siemens TIM 4R-IE (6NH7800-4BA00) Siemens TIM 4R-IE DNP3 (6NH7803-4BA00-0AA0)
    affected: workaround, no fix planned

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

cisa ICSA-15-356-01 updated cvss 5.3

Siemens RUGGEDCOM ROX-based Devices NTP Vulnerabilities

  • Siemens ROX II <2.9.0 Siemens RUGGEDCOM ROX I
    affected: mitigation “Update to the latest version. (http://www.siemens.com/automation/support-request)”

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

Exploit prediction

81.76% chance of exploitation in the next 30 days, higher than 99.6% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.