CVE-2015-7871

highpriority · attend · 78EPSS 0.818 · 100 %ileexploit · functionalDEEURUUS

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

1 exploit · functional

Likely / severe?

81.8% (100th) EPSS

CVSS 7.5 · high

Is it mine?

31 products

Check your exposure

Who says so?

7 sources

cnnvd · enisa_euvd · fstec_bdu · auma_psirt

EPSS · scored 2026-10-23

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.

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

FixedSIMA² Master Stationauma_psirt
Upgrade your SIMA2 to software version 2.6 or above. The NTP service of the SIMA2 Master Station with software version V2.6 and above includes a current, supported version of ntpd.
MitigationSIMA² Master Stationauma_psirt
1. If your SIMA2 does not need to provide time information to other systems or synchronize itself with an NTP server, disable the NTP client on those systems. Please note that the NTP client is disabled by default in SIMA2 2. In case you must use the NTP server on an SIMA2, choose from the following options to reduce NTP-based risks: - Allow NTP traffic to/from trusted NTP clients only - Monitor the network for malicious NTP traffic going to/coming from the SIMA2 - Filter malicious NTP traffic going to/coming from the SIMA2 Monitor NTP server operations on your SIMA2 (server availability, correctness of advertised time, NTP-related log entries, etc.) 3. In case you must use the NTP client on an SIMA2, choose from the following options to reduce NTP-based risks: - Use trusted NTP servers only - Allow NTP traffic to/from trusted NTP servers only - Monitor the network for malicious NTP traffic targeting the SIMA2 - Filter malicious NTP traffic targeting the SIMA2 - Monitor NTP client operations on your SIMA2 (correctness of system time, NTP-related log entries, etc.)
MitigationROX IIcisa_csaf_ot
Update to the latest version. (http://www.siemens.com/automation/support-request)
http://www.siemens.com/automation/support-request
MitigationRUGGEDCOM ROX Icisa_csaf_ot
Update to the latest version. (http://www.siemens.com/automation/support-request)
http://www.siemens.com/automation/support-request
WorkaroundSIPLUS NET TIM 4R-IE (6AG1800-4BA00-7AA0)siemens_psirt
Configure an additional firewall to prevent communication to the port udp/123 of an affected device.
WorkaroundSIPLUS NET TIM 4R-IE DNP3 (6AG1803-4BA00-7AA0)siemens_psirt
Configure an additional firewall to prevent communication to the port udp/123 of an affected device.
WorkaroundTIM 4R-IE (6NH7800-4BA00)siemens_psirt
Configure an additional firewall to prevent communication to the port udp/123 of an affected device.
WorkaroundTIM 4R-IE DNP3 (6NH7803-4BA00-0AA0)siemens_psirt
Configure an additional firewall to prevent communication to the port udp/123 of an affected device.
WorkaroundSIPLUS NET TIM 4R-IE (6AG1800-4BA00-7AA0)cisa_csaf_ot
Configure an additional firewall to prevent communication to the port udp/123 of an affected device.
WorkaroundSIPLUS NET TIM 4R-IE DNP3 (6AG1803-4BA00-7AA0)cisa_csaf_ot
Configure an additional firewall to prevent communication to the port udp/123 of an affected device.
WorkaroundTIM 4R-IE (6NH7800-4BA00)cisa_csaf_ot
Configure an additional firewall to prevent communication to the port udp/123 of an affected device.
WorkaroundTIM 4R-IE DNP3 (6NH7803-4BA00-0AA0)cisa_csaf_ot
Configure an additional firewall to prevent communication to the port udp/123 of an affected device.
No fix plannedSIPLUS NET TIM 4R-IE (6AG1800-4BA00-7AA0)siemens_psirt
Currently no fix is planned
No fix plannedSIPLUS NET TIM 4R-IE DNP3 (6AG1803-4BA00-7AA0)siemens_psirt
Currently no fix is planned
No fix plannedTIM 4R-IE (6NH7800-4BA00)siemens_psirt
Currently no fix is planned
No fix plannedTIM 4R-IE DNP3 (6NH7803-4BA00-0AA0)siemens_psirt
Currently no fix is planned
No fix plannedSIPLUS NET TIM 4R-IE (6AG1800-4BA00-7AA0)cisa_csaf_ot
Currently no fix is planned
No fix plannedSIPLUS NET TIM 4R-IE DNP3 (6AG1803-4BA00-7AA0)cisa_csaf_ot
Currently no fix is planned
No fix plannedTIM 4R-IE (6NH7800-4BA00)cisa_csaf_ot
Currently no fix is planned
No fix plannedTIM 4R-IE DNP3 (6NH7803-4BA00-0AA0)cisa_csaf_ot
Currently no fix is planned

cvss

Technical severity, 0–10. One row per scoring source.

9.8

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–critical · 5.3–9.8

v2.07.5highAV:N/AC:L/Au:N/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 10 · impact 6.4

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 5.9

v2.07.5highAV:N/AC:L/Au:N/C:P/I:P/A:Psecondary · FSTEC (BDU) RU

v3.05.3mediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:Nsecondary · CISA US

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · CISA US

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · Siemens ProductCERT DE

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:Hsecondary · CVSS-BT (t0sche)

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · AUMA PSIRT

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-287USprimaryCWE-287USCWE-287USCWE-287USCWE-287USCWE-592US

exploits (1)

Public proof-of-concept and weaponised exploit code.

auxiliary/scanner/ntp/ntp_nak_to_the_futureNTP "NAK to the Future"functional · metasploit

affected products (31)

Products and version ranges known to be affected.

AUMA SIMA² Master Stationall versionsfixedauma_psirtDE
AUMA SIMA² Master Station< V2.6auma_psirtDE
SIPLUS NET TIM 4R-IE (6AG1800-4BA00-7AA0)all versionscisa_csaf_otUS
SIPLUS NET TIM 4R-IE DNP3 (6AG1803-4BA00-7AA0)all versionscisa_csaf_otUS
TIM 4R-IE (6NH7800-4BA00)all versionscisa_csaf_otUS
TIM 4R-IE DNP3 (6NH7803-4BA00-0AA0)all versionscisa_csaf_otUS
Siemens ROX II< 2.9.0cisa_csaf_otUS
Siemens RUGGEDCOM ROX I≤ vers:all/*cisa_csaf_otUS
Siemens SIPLUS NET TIM 4R-IE (6AG1800-4BA00-7AA0)≤ vers:all/*cisa_csaf_otUS
Siemens SIPLUS NET TIM 4R-IE DNP3 (6AG1803-4BA00-7AA0)≤ vers:all/*cisa_csaf_otUS
Siemens TIM 4R-IE (6NH7800-4BA00)≤ vers:all/*cisa_csaf_otUS
Siemens TIM 4R-IE DNP3 (6NH7803-4BA00-0AA0)≤ vers:all/*cisa_csaf_otUS
n/a n/a≤ n/aenisa_euvdEU
Network Time Foundation NTP4.2 → 4.2.8p4fstec_bduRU
Network Time Foundation NTP4.3 → 4.3.77fstec_bduRU
debian debian linux= 7.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
debian debian linux= 8.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
debian debian linux= 9.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
netapp clustered data ontapall versionsnvdUScpe:2.3:o:netapp:clustered_data_ontap:*:*:*:*:*:*:*:*
netapp data ontapall versionsnvdUScpe:2.3:o:netapp:data_ontap:*:*:*:*:*:*:*:*

showing 20 of 31

advisories (4)

Vendor and ecosystem advisories describing this.

SSA-497656SSA-497656: Multiple NTP Vulnerabilities in TIM 4R-IE Devices2021-04-13csaf · siemens_psirtDE
TIM 4R-IE devices contain multiple vulnerabilities in the integrated NTP component as listed below. Siemens recommends specific countermeasures for products where fixes are not, or not yet available.
VDE-2022-032AUMA: Multiple Vulnerabilities in Automation Runtime NTP Service2022-08-09csaf · auma_psirtDE
The SIMA2 Master Station features an NTP service based on ntpd, a reference implementation of the Network Time Protocol (NTP). Affected SIMA2 Master Stations with software version < V2.6 include an outdated version of ntpd which is affected by a large number of vulnerabilities
ICSA-15-356-01Siemens RUGGEDCOM ROX-based Devices NTP Vulnerabilities2015-09-24icsa · cisa_csaf_otUS
This CSAF advisory was extracted from unstructured data and may contain inaccuracies. If you notice any errors, please reach out to the designated contact at CISA CSAF: central@cisa.dhs.gov
ICSA-21-103-11Siemens TIM 4R-IE Devices2021-04-13icsa · cisa_csaf_otUS
TIM 4R-IE devices contain multiple vulnerabilities in the integrated NTP component as listed below. Siemens recommends specific countermeasures for products where fixes are not, or not yet available.

also known as (7)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu auma_psirt cisa_csaf_ot nvd siemens_psirt NVD CVE.org MITRE

published 2017-08-07modified 2026-06-17

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references (31)

External citations — patches, advisories, analysis.

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