CVE-2015-7691

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 7.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2017-08-07 · updated 2026-06-17
Weakness: CWE-20

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.

Affected products

Debian Linux: 7.0, 8.0, 9.0
Clustered Data ONTAP: all versions
NetApp Data ONTAP operating in 7-Mode: all versions
NetApp Oncommand Performance Manager: all versions
NetApp OnCommand Unified Manager for 7-Mode (core package): all versions
NTP: from 4.2.0 before 4.2.8; from 4.3.0 before 4.3.77; 4.2.8, 4.2.8-p1, 4.2.8-p1-beta1, 4.2.8-p1-beta2, 4.2.8-p1-beta3, 4.2.8-p1-beta4 (+11) — fixed in 4.2.8, 4.3.77
Oracle Corporation Oracle Linux: 6
RedHat Enterprise Linux Desktop: 6.0, 7.0
RedHat Enterprise Linux Server: 6.0, 7.0
RedHat Enterprise Linux Server Aus: 7.3, 7.4, 7.6, 7.7
RedHat Enterprise Linux Server Eus: 7.3, 7.4, 7.5, 7.6, 7.7
RedHat Enterprise Linux Server Tus: 7.3, 7.6, 7.7
RedHat Enterprise Linux Workstation: 6.0, 7.0

How to fix

Upgrade to a fixed version: NTP 4.2.8, 4.3.77. Check the vendor advisory for mitigations.

References

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