In an Segment Routing ISIS (SR-ISIS)/MPLS environment, on Juniper Networks Junos OS and Junos OS Evolved devices, configured with ISIS Flexible Algorithm for Segment Routing and sensor-based statistics, a flap of a ISIS link in the network, can lead to a routing process daemon (RPD) crash and restart, causing a Denial of Service (DoS). Continued link flaps will create a sustained Denial of Service (DoS) condition.
This issue affects:
Juniper Networks Junos OS:
Juniper Networks Junos OS Evolved:
This issue does not affect:
Juniper Networks Junos OS releases prior to 19.4R1.
Juniper Networks Junos OS Evolved releases prior to 19.4R1-EVO.
The two config stanzas required to be affected by this issue are shown below:
[ routing-options flex-algorithm <name> ]
[ protocols isis source-packet-routing sensor-based-stats per-sid egress ]
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-2021-0287 .
The following software releases have been updated to resolve this specific issue:
Junos OS: 19.4R1-S4, 19.4R3-S2, 20.1R2-S1, 20.1R3, 20.2R2-S2, 20.2R3, 20.3R2, 20.4R1, and all subsequent releases.
Junos OS Evolved: 20.3R2-EVO, 20.4R2-EVO, 21.1R1-EVO, and all subsequent releases.
This issue is being tracked as 1555627 .
Software releases or updates are available for download at https://support.juniper.net/support/downloads/
Configuration of IS-IS Flexible Algorithm for Segment Routing or sensor-based statistics can be disabled to mitigate this issue.
2021-07-14: Initial Publication.