CVE-2021-0287: Junos OS and Junos OS Evolved: RPD could crash in SR-ISIS/MPLS environment due to a flap of an ISIS link in the network

Severity: medium (CVSS 5.7 v2.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-07-15 · updated 2026-06-17
Weakness: CWE-754

Description

In a 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: 19.4 versions prior to 19.4R1-S4, 19.4R3-S2; 20.1 versions prior to 20.1R2-S1, 20.1R3; 20.2 versions prior to 20.2R2-S2, 20.2R3; 20.3 versions prior to 20.3R2; Juniper Networks Junos OS Evolved: 20.3-EVO versions prior to 20.3R2-EVO; 20.4-EVO versions prior to 20.4R2-EVO. 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.

Affected products

Juniper Junos OS: 19.4-r1, 19.4-r1-s1, 19.4-r1-s2, 19.4-r1-s3, 19.4-r2, 19.4-r2-s1 (+18)
Juniper Networks Junos OS Evolved: 20.3, 20.3-r1, 20.4-r1-s1

References

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