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

MEDIUM

6.5

CVSS Score

Published: July 15, 2021 at 08:01 PM UTC

Updated: June 17, 2026 at 03:29 AM UTC

3 products affected across 2 vendorsJunosJunos OS EvolvedJunos OS Evolved

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Severity

MEDIUM6.5

Exploit prediction

EPSS 0.4%

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Junos OS Evolved · Juniper

95%

20.3 20.3 r1 20.4 r1-s1

Junos · Juniper Networks

95%

19.4R1 ≤ v < 19.4*20.1 ≤ v < 20.1R2-S1, 20.1R320.2 ≤ v < 20.2R2-S2, 20.2R320.3 ≤ v < 20.3R219.4 r1 19.4 r1-s1 19.4 r1-s2 19.4 r1-s3 19.4 r2 19.4 r2-s1 19.4 r2-s2 19.4 r2-s3 19.4 r3 19.4 r3-s1 19.4R1 20.1 20.1 r1 20.1 r1-s1 20.1 r1-s2 20.1 r1-s3 20.1 r1-s4 20.1 r2 20.2 20.2 r1 20.2 r1-s1 20.2 r1-s2 20.2 r1-s3 20.2 r2 20.2 r2-s1 20.3 20.3 r1 20.3 r1-s1

Affected range stops below 19.4*, so it looks safe — our inference, not a vendor statement

Vendor states this is fixed in 19.4R1 (unaffected)

Affected range stops below 20.1R2-S1, 20.1R3, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.2R2-S2, 20.2R3, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.3R2, so it looks safe — our inference, not a vendor statement

Junos OS Evolved · Juniper Networks

60%

19.4R1-EVO ≤ v < 19.4*20.1R1-EVO ≤ v < 20.1*20.2R1-EVO ≤ v < 20.2*20.3 ≤ v < 20.3R2-EVO20.4 ≤ v < 20.4R2-EVO19.4R1-EVO 20.1R1-EVO 20.2R1-EVO 20.3 20.4

Affected range stops below 19.4*, so it looks safe — our inference, not a vendor statement

Vendor states this is fixed in 19.4R1-EVO (unaffected)

Affected range stops below 20.1*, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.2*, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.3R2-EVO, so it looks safe — our inference, not a vendor statement

Affected range stops below 20.4R2-EVO, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://kb.juniper.net/JSA11189

References (1)

x_refsource_CONFIRMVendor Advisory

Source: [email protected]

https://kb.juniper.net/JSA11189

CVSS

6.5MEDIUMjuniper

Attack Vector: ADJACENT_NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusMODIFIED

CWE

CWE-754

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