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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
Resolution:        Patch/Upgrade
CVE Names:         CVE-2019-8936  

Reference:         ESB-2021.1346

Original Bulletin: 

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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

Product Affected:
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:

[system ntp]

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
subsequent releases.

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://
Modification History:

2021-07-14: Initial Publication.

CVSS Score:
7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Severity Level:
Severity Assessment:
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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