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             AUSCERT External Security Bulletin Redistribution

JSA11161 - 2021-04 Security Bulletin: Junos OS: PTX Series, QFX10K Series:
              A PTX/QFX FPC may restart unexpectedly with the
        "inline-Jflow" feature enabled on a large-scale deployment
                               15 April 2021


        AusCERT Security Bulletin Summary

Product:           Junos OS: PTX Series
                   Junos OS: QFX10K Series
Publisher:         Juniper Networks
Operating System:  Juniper
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-0270  

Original Bulletin: 

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2021-04 Security Bulletin: Junos OS: PTX Series, QFX10K Series:
A PTX/QFX FPC may restart unexpectedly with the "inline-Jflow" feature
enabled on a large-scale deployment (CVE-2021-0270)

Article ID  : JSA11161
Last Updated: 14 Apr 2021
Version     : 4.0

Product Affected:
This issue affects Junos OS 18.1. Affected platforms: PTX Series, QFX10K


On PTX Series and QFX10k Series devices with the "inline-jflow" feature
enabled, a use after free weakness in the Packet Forwarding Engine (PFE)
microkernel architecture of Juniper Networks Junos OS may allow an attacker to
cause a Denial of Service (DoS) condition whereby one or more Flexible PIC
Concentrators (FPCs) may restart. As this is a race condition situation this
issue become more likely to be hit when network instability occurs, such as but
not limited to BGP/IGP reconvergences, and/or further likely to occur when more
active "traffic flows" are occurring through the device. When this issue
occurs, it will cause one or more FPCs to restart unexpectedly. During FPC
restarts core files will be generated. While the core file is generated traffic
will be disrupted. Sustained receipt of large traffic flows and
reconvergence-like situations may sustain the Denial of Service (DoS)

This issue affects:

Juniper Networks Junos OS:

  o 18.1 version 18.1R2 and later versions prior to 18.1R3-S10 on PTX Series,
    QFX10K Series.

The inline flow monitoring configuration can be broadly classified into the
following categories:

Configurations at the [edit services flow-monitoring version-ipfix template] or
[edit services flow-monitoring version9 template] hierarchy level-At this
level, you configure the template properties for inline flow monitoring.

Configurations at the [edit forwarding-options sampling instance] hierarchy
level-At this level, you configure a sampling instance and associate the
template to the sampling instance. At this level, you also configure the
flow-server IP address and port number as well as the autonomous system type.

Configurations at the [edit chassis fpc] hierarchy level-At this level, you
associate the sampling instance with the FPC on which the media interface is

Configurations at the [edit firewall] hierarchy level-At this level you
configure a firewall filter for the family of traffic to be sampled. You must
attach this filter to the interface on which you want to sample the traffic.

See https://www.juniper.net/documentation/en_US/junos/topics/task/configuration
/inline-flow-monitoring-ptx.html for further details.

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-2021-0270 .


The following software releases have been updated to resolve this specific
issue: 16.1R7-S8, 17.2R3-S4, 17.3R3-S8, 17.4R2-S11, 17.4R3-S2, 18.1R3-S10,
18.2R1, and all subsequent releases.

This issue is being tracked as 1498427 .


If you are susceptible to this issue and unable to upgrade to software with the
fix, you can deploy a workaround by disabling the "inline-flow" feature.

To check for use and to disable the "inline-jflow" service on a device, see
inline-flow-monitoring-ptx.html for additional details.

Removing "inline-jflow" takes effect immediately and there is no need to
restart the FPCs or the router. Once the feature is removed, the router no
longer provides traffic data to the flow collector.

Software releases or updates are available for download at https://
Modification History:

2021-04-14: Initial Publication.
2021-04-14: Added QFX after PTX on FPC.

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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