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AUSCERT External Security Bulletin Redistribution
JSA11179 - 2021-07 Security Bulletin: Junos OS Evolved:
Authenticated denial of service in ntpd (CVE-2019-8936)
15 July 2021
AusCERT Security Bulletin Summary
Product: Junos OS Evolved
Publisher: Juniper Networks
Operating System: Juniper
Impact/Access: Denial of Service -- Existing Account
CVE Names: CVE-2019-8936
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2021-07 Security Bulletin: Junos OS Evolved: Authenticated denial of service in ntpd (CVE-2019-8936)
Article ID : JSA11179
Last Updated: 14 Jul 2021
Version : 2.0
This issue affects Junos OS Evolved All versions prior to 20.4, 21.1, 21.2.
On Juniper Networks Junos OS Evolved devices where ntp is enabled a crafted
malicious authenticated mode 6 packet from a permitted network address can
trigger a NULL pointer dereference. Note for this attack to work, the sending
system must be on an address from which the target ntpd accepts mode 6 packets,
and must use a private key that is specifically listed as being used for mode 6
authorization. The ntpd daemon can crash due to the NULL pointer dereference,
causing a Denial of Service (DoS).
Continued receipt and processing of these crafted malicious packets will create
a sustained Denial of Service (DoS) condition.
This issue affects:
Juniper Networks Junos OS Evolved
o All versions prior to 20.4R2-S2-EVO;
o 21.1 versions prior to 21.1R2-EVO;
o 21.2 versions prior to 21.2R1-EVO.
The following minimal configuration example is provided:
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
This issue was discovered during external security research.
This issue has been assigned CVE-2019-8936 .
The following software releases have been updated to resolve this specific
issue: Junos OS Evolved: 20.4R2-S2-EVO, 21.1R2-EVO, 21.2R1-EVO, and all
This issue is being tracked as 1589449 .
Use 'restrict noquery' options in the ntpd configuration to limit addresses
that can send mode 6 queries.
Software releases or updates are available for download at https://
2021-07-14: Initial Publication.
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common
Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."
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