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2021-04 Security Bulletin: Junos OS: PTX Series, QFX Series: Due to a race condition input loopback firewall filters applied to interfaces may not operate even when listed in the running configuration. (CVE-2021-0247)

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Article ID: JSA11140 SECURITY_ADVISORIES Last Updated: 15 Apr 2021Version: 2.0
Product Affected:
This issue affects Junos OS 14.1, 14.1X53, 15.1, 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. Affected platforms: PTX Series, QFX Series.
Problem:

A Race Condition (Concurrent Execution using Shared Resource with Improper Synchronization) vulnerability in the firewall process (dfwd) of Juniper Networks Junos OS allows an attacker to bypass the firewall rule sets applied to the input loopback filter on any interfaces of a device.

This issue is detectable by reviewing the PFE firewall rules, as well as the firewall counters and seeing if they are incrementing or not.

For example:

show firewall
Filter: __default_bpdu_filter__
Filter: FILTER-INET-01
Counters:
Name Bytes Packets
output-match-inet 0 0 <<<<<< missing firewall packet count

This issue affects:

Juniper Networks Junos OS:

  • 14.1X53 versions prior to 14.1X53-D53 on QFX Series;
  • 14.1 versions 14.1R1 and later versions prior to 15.1 versions prior to 15.1R7-S6 on QFX Series, PTX Series;
  • 15.1X53 versions prior to 15.1X53-D593 on QFX Series;
  • 16.1 versions prior to 16.1R7-S7 on QFX Series, PTX Series;
  • 16.2 versions prior to 16.2R2-S11, 16.2R3 on QFX Series, PTX Series;
  • 17.1 versions prior to 17.1R2-S11, 17.1R3-S2 on QFX Series, PTX Series;
  • 17.2 versions prior to 17.2R1-S9, 17.2R3-S3 on QFX Series, PTX Series;
  • 17.3 versions prior to 17.3R2-S5, 17.3R3-S7 on QFX Series, PTX Series;
  • 17.4 versions prior to 17.4R2-S9, 17.4R3 on QFX Series, PTX Series;
  • 18.1 versions prior to 18.1R3-S9 on QFX Series, PTX Series;
  • 18.2 versions prior to 18.2R2-S6, 18.2R3-S3 on QFX Series, PTX Series;
  • 18.3 versions prior to 18.3R1-S7, 18.3R2-S3, 18.3R3-S1 on QFX Series, PTX Series;
  • 18.4 versions prior to 18.4R1-S5, 18.4R2-S3, 18.4R3 on QFX Series, PTX Series;
  • 19.1 versions prior to 19.1R1-S4, 19.1R2-S1, 19.1R3 on QFX Series, PTX Series;
  • 19.2 versions prior to 19.2R1-S3, 19.2R2 on QFX Series, PTX Series.

This issue impact all filters families (inet, inet6, etc.) yet only on input loopback filters.

It does not does not rely upon the location where a filter is set, impacting both logical and physical interfaces.

Configuration examples for input filtering are posted on the support site and in product documentation.

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was seen during production usage.

This issue has been assigned CVE-2021-0247.

Solution:

The following software releases have been updated to resolve this specific issue: Junos OS 14.1X53-D53, 15.1R7-S6, 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-S3, 18.4R3, 19.1R1-S4, 19.1R2-S1, 19.1R3, 19.2R1-S3, 19.2R2, 19.3R1, and all subsequent releases.

This issue is being tracked as 1430385.

Workaround:
There are no viable workarounds for this issue.
Implementation:
Software releases or updates are available for download at https://support.juniper.net/support/downloads/
Modification History:
2021-04-14: Initial Publication.
2021-04-15: Removed spurious 18.4R2-S7 release entry in problem description.
CVSS Score:
5.1 (CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:C/C:L/I:L/A:L)
Severity Level:
Medium
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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