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AUSCERT External Security Bulletin Redistribution
JSA11140 - 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.
16 April 2021
AusCERT Security Bulletin Summary
Product: Junos OS: PTX Series
Junos OS: QFX Series
Publisher: Juniper Networks
Operating System: Juniper
Impact/Access: Unauthorised Access -- Existing Account
CVE Names: CVE-2021-0247
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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)
Article ID : JSA11140
Last Updated: 15 Apr 2021
Version : 2.0
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.
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.
Name Bytes Packets
output-match-inet 0 0 <<<<<< missing firewall packet count
This issue affects:
Juniper Networks Junos OS:
o 14.1X53 versions prior to 14.1X53-D53 on QFX Series;
o 14.1 versions 14.1R1 and later versions prior to 15.1 versions prior to
15.1R7-S6 on QFX Series, PTX Series;
o 15.1X53 versions prior to 15.1X53-D593 on QFX Series;
o 16.1 versions prior to 16.1R7-S7 on QFX Series, PTX Series;
o 16.2 versions prior to 16.2R2-S11, 16.2R3 on QFX Series, PTX Series;
o 17.1 versions prior to 17.1R2-S11, 17.1R3-S2 on QFX Series, PTX Series;
o 17.2 versions prior to 17.2R1-S9, 17.2R3-S3 on QFX Series, PTX Series;
o 17.3 versions prior to 17.3R2-S5, 17.3R3-S7 on QFX Series, PTX Series;
o 17.4 versions prior to 17.4R2-S9, 17.4R3 on QFX Series, PTX Series;
o 18.1 versions prior to 18.1R3-S9 on QFX Series, PTX Series;
o 18.2 versions prior to 18.2R2-S6, 18.2R3-S3 on QFX Series, PTX Series;
o 18.3 versions prior to 18.3R1-S7, 18.3R2-S3, 18.3R3-S1 on QFX Series, PTX
o 18.4 versions prior to 18.4R1-S5, 18.4R2-S3, 18.4R3 on QFX Series, PTX
o 19.1 versions prior to 19.1R1-S4, 19.1R2-S1, 19.1R3 on QFX Series, PTX
o 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
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 .
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 .
There are no viable workarounds for this issue.
Software releases or updates are available for download at https://
2021-04-14: Initial Publication.
2021-04-15: Removed spurious 18.4R2-S7 release entry in problem description.
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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