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

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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.
Problem:

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

Solution:

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.

Workaround:
Use 'restrict noquery' options in the ntpd configuration to limit addresses that can send mode 6 queries.
Implementation:
Software releases or updates are available for download at https://support.juniper.net/support/downloads/
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:
High
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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