How severe is CVE-2015-7691?

CVE-2015-7691 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2015-7691 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2015-7691?

CVE-2015-7691 primarily affects Ntp. In total, 44 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2015-7691?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2015-7691 published?

CVE-2015-7691 was published on 2017-08-07 and last updated on 2026-06-17.

CVE-2015-7691

CVE-2015-7691 is a high-severity vulnerability in Ntp with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 7% (93rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Ntp
Published: 2017-08-07
Last modified: 2026-06-17

Description

The crypto_xmit function in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to cause a denial of service (crash) via crafted packets containing particular autokey operations. NOTE: This vulnerability exists due to an incomplete fix for CVE-2014-9750.

Frequently asked questions

What is CVE-2015-7691?: The crypto_xmit function in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to cause a denial of service (crash) via crafted packets containing particular autokey operations. NOTE: This vulnerability exists due to an incomplete fix for CVE-2014-9750.
How severe is CVE-2015-7691?: CVE-2015-7691 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2015-7691 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2015-7691?: CVE-2015-7691 primarily affects Ntp. In total, 44 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2015-7691?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2015-7691 published?: CVE-2015-7691 was published on 2017-08-07 and last updated on 2026-06-17.

References

Affected products (44)

cpe:2.3:a:ntp:ntp:*:*:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:-:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p1:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p1-beta1:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p1-beta2:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p1-beta3:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p1-beta4:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p1-beta5:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p1-rc1:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p1-rc2:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p2:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p2-rc1:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p2-rc2:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p2-rc3:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p3:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p3-rc1:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p3-rc2:*:*:*:*:*:*
cpe:2.3:a:ntp:ntp:4.2.8:p3-rc3:*:*:*:*:*:*
cpe:2.3:o:oracle:linux:6:-:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:7.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:a:netapp:oncommand_performance_manager:-:*:*:*:*:*:*:*
cpe:2.3:a:netapp:oncommand_unified_manager:-:*:*:*:*:clustered_data_ontap:*:*
cpe:2.3:o:netapp:clustered_data_ontap:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:data_ontap:-:*:*:*:*:7-mode:*:*
cpe:2.3:o:redhat:enterprise_linux_desktop:6.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_desktop:7.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server:6.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server:7.0:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_aus:7.3:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_aus:7.4:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_aus:7.6:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_aus:7.7:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_eus:7.3:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_eus:7.4:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_eus:7.5:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_eus:7.6:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_eus:7.7:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux_server_tus:7.3:*:*:*:*:*:*:*

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CVE-2015-7853 — Critical (CVSS 9.8): The datalen parameter in the refclock driver in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote…
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CVE-2015-7854 — High (CVSS 8.8): Buffer overflow in the password management functionality in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows…

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Threat intelligence

Threat-intel indicators referencing this CVE:

197.248.207.139 (ipv4-addr)
135.129.128.247 (ipv4-addr)
119.201.59.224 (ipv4-addr)
42.200.60.186 (ipv4-addr)
223.197.153.135 (ipv4-addr)
125.212.244.35 (ipv4-addr)
202.29.220.126 (ipv4-addr)
93.42.227.251 (ipv4-addr)