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2021-04 Security Bulletin: Junos OS: FreeBSD-SA-19:04.ntp : Authenticated denial of service in ntpd (CVE-2019-8936)



Article ID: JSA11115 SECURITY_ADVISORIES Last Updated: 14 Apr 2021Version: 4.0
Product Affected:
This issue affects Junos OS 12.3, 12.3X48, 14.1X53, 15.1, 15.1X49, 15.1X53, 16.1, 16.2, 17.1, 17.2, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3.

On Juniper Networks Junos OS 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:

  • 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, 14.1X53-D140 on EX Series;
  • 15.1 versions prior to 15.1R7-S6;
  • 15.1X49 versions prior to 15.1X49-D200 on SRX Series;
  • 15.1X53 versions prior to 15.1X53-D593 on EX2300 Series, EX3400 Series;
  • 16.1 versions prior to 16.1R7-S7;
  • 16.2 versions prior to 16.2R2-S11, 16.2R3;
  • 17.1 versions prior to 17.1R2-S11, 17.1R3-S2;
  • 17.2 versions prior to 17.2R1-S9, 17.2R3-S3;
  • 17.3 versions prior to 17.3R2-S5, 17.3R3-S7;
  • 17.4 versions prior to 17.4R2-S9, 17.4R3;
  • 18.1 versions prior to 18.1R3-S9;
  • 18.2 versions prior to 18.2R2-S6, 18.2R3-S3;
  • 18.3 versions prior to 18.3R1-S7, 18.3R2-S3, 18.3R3-S1;
  • 18.4 versions prior to 18.4R1-S5, 18.4R2-S4, 18.4R3;
  • 19.1 versions prior to 19.1R1-S4, 19.1R2-S1, 19.1R3;
  • 19.2 versions prior to 19.2R1-S3, 19.2R2;
  • 19.3 versions prior to 19.3R1-S1, 19.3R2-S1, 19.3R3.

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 a external security research.

This issue has been assigned CVE-2019-8936


The following software releases have been updated to resolve this specific issue: 12.3R12-S15, 12.3X48-D95, 14.1X53-D53, 14.1X53-D140, 15.1R7-S6, 15.1X49-D200, 15.1X53-D593, 16.1R7-S7, 16.2R2-S11, 16.2R3, 17.1R2-S11, 17.1R3-S2, 17.2R1-S9, 17.2R3-S3, 17.3R2-S5, 17.3R3-S7, 17.4R2-S9, 17.4R3, 18.1R3-S9, 18.2R2-S6, 18.2R3-S3, 18.3R1-S7, 18.3R2-S3, 18.3R3-S1, 18.4R1-S5, 18.4R2-S4, 18.4R3, 19.1R1-S4, 19.1R2-S1, 19.1R3, 19.2R1-S3, 19.2R2, 19.3R1-S1, 19.3R2-S1, 19.3R3, 19.4R1, and all subsequent releases.

This issue is being tracked as 1436892.

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
Modification History:
2021-04-14: 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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