Support Support Downloads Knowledge Base Juniper Support Portal Community

Knowledge Base

Search our Knowledge Base sites to find answers to your questions.

Ask All Knowledge Base Sites All Knowledge Base Sites JunosE Defect (KA)Knowledge BaseSecurity AdvisoriesTechnical BulletinsTechnotes Sign in to display secure content and recently viewed articles

2021-04 Security Bulletin: Junos OS and Junos OS Evolved: Multiple NTP vulnerabilities resolved.



Article ID: JSA11171 SECURITY_ADVISORIES Last Updated: 14 Apr 2021Version: 1.0
Product Affected:
These issues affect Junos OS 12.3, 12.3X48, 14.1X53, 15.1, 15.1X49, 16.1, 16.2, 17.1, 17.2, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2. These issues affect Junos OS Evolved.

Multiple NTP vulnerabilities have been resolved in Juniper Networks Junos OS and Junos OS Evolved by updating third party software where vulnerabilities were found during external security research.

These issues affect:

Juniper Networks Junos OS:

  • 12.3 versions prior to 12.3R12-S15 on EX Series;
  • 12.3X48 versions prior to 12.3X48-D95 on SRX Series;
  • 14.1X53 versions prior to 14.1X53-D53;
  • 15.1 versions prior to 15.1R7-S6 on EX Series;
  • 15.1X49 versions prior to 15.1X49-D190 on SRX Series;
  • 16.1 versions prior to 16.1R7-S6;
  • 16.2 versions prior to 16.2R3;
  • 17.1 versions prior to 17.1R2-S11, 17.1R3-S1;
  • 17.2 versions prior to 17.2R1-S9, 17.2R2-S8, 17.2R3-S3;
  • 17.3 versions prior to 17.3R2-S5, 17.3R3-S6;
  • 17.4 versions prior to 17.4R2-S7, 17.4R3;
  • 18.1 versions prior to 18.1R3-S8;
  • 18.2 versions prior to 18.2R2-S7, 18.2R3-S1;
  • 18.3 versions prior to 18.3R1-S5, 18.3R2-S2, 18.3R3;
  • 18.4 versions prior to 18.4R1-S4, 18.4R2-S1, 18.4R3;
  • 19.1 versions prior to 19.1R1-S3, 19.1R2;
  • 19.2 versions prior to 19.2R1-S1, 19.2R2.
Juniper Networks Junos OS Evolved
  • All versions prior to 20.1R1-EVO.

NTP must be operating on the device to be affected by these issues, for example, the following minimal configuration is necessary:

[set system ntp]

Juniper SIRT is not aware of any malicious exploitation of these vulnerabilities.

These issues were discovered during a external security research.

Important security issues resolved include:

CVE CVSS Summary
CVE-2016-9310 6.5 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L) The control mode (mode 6) functionality in ntpd in NTP before 4.2.8p9 allows remote attackers to set or unset traps via a crafted control mode packet.
CVE-2013-5211 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P The monlist feature in ntp_request.c in ntpd in NTP before 4.2.7p26 allows remote attackers to cause a denial of service (traffic amplification) via forged (1) REQ_MON_GETLIST or (2) REQ_MON_GETLIST_1 requests, as exploited in the wild in December 2013.

The following software releases have been updated to resolve these specific issues:

Junos OS: 12.3R12-S15, 12.3X48-D95, 14.1X53-D53, 15.1R7-S6, 15.1X49-D190, 16.1R7-S6, 16.2R3, 17.1R2-S11, 17.1R3-S1, 17.2R1-S9, 17.2R2-S8, 17.2R3-S3, 17.3R2-S5, 17.3R3-S6, 17.4R2-S7, 17.4R3, 18.1R3-S8, 18.2R2-S7, 18.2R3-S1, 18.3R1-S5, 18.3R2-S2, 18.3R3, 18.4R1-S4, 18.4R2-S1, 18.4R3, 19.1R1-S3, 19.1R2, 19.2R1-S1, 19.2R2, 19.3R1 and all subsequent releases.

Junos OS Evolved: 20.1R1-EVO, and subsequent releases.

After upgrading to a resolved release, the mitigations listed in the following advisories also need to be applied:

  • JSA10613
  • JSA10663
  • JSA10898
  • JSA10711
  • JSA10776

Then, the CLI must be configured using the ntp restrict command:

set system ntp restrict <address> mask <mask_addr> noquery

Note 1: With the above configuration all masked source addresses (source_address & mask_addr) which matches with (address & mask_addr) are restricted to query ntpq/ntpdc to ntp server.

Note 2: The restriction of subnets is only available from Junos OS 20.1R1, and subsequent releases, and Junos OS Evolved 20.2R1-EVO, and subsequent releases.

An Example Configuration which allows all the hosts having address 192.168.0.<0-255> being unable to send ntpq/ntpdc query to ntp server from Junos OS 20.1R1, and onward, and Junos OS Evolved 20.2R1-EVO, and onward:

set system ntp restrict mask noquery

Note 3: The noquery option is a hidden command in all releases prior to Junos OS 20.1R1. The command may not persist across reboots, so care must be taken to ensure that it is written to the ntp configuration file. Contact Juniper Networks Technical Assistance Center (JTAC) for guided assistance if necessary.

If any of the above NTP mitigations are not in place, there is still the possibility of exploitability.

This issue is being tracked as 1446493 and 1446497.


Use firewall filters to block NTP mode 6 query packets.

Software releases or updates are available for download at
Modification History:
2021-04-14: Initial Publication.
CVSS Score:
6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L)
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."

Related Links

Comment on this article > Affected Products Browse the Knowledge Base for more articles related to these product categories. Select a category to begin.

Getting Up and Running with Junos

Getting Up and Running with Junos Security Alerts and Vulnerabilities Product Alerts and Software Release Notices Problem Report (PR) Search Tool EOL Notices and Bulletins JTAC User Guide Customer Care User Guide Pathfinder SRX High Availability Configurator SRX VPN Configurator Training Courses and Videos End User Licence Agreement Global Search