CVE-2021-31363

Junos OS and Junos OS Evolved: Receipt of a specific LDP message will cause a Denial of Service

Description

In an MPLS P2MP environment a Loop with Unreachable Exit Condition vulnerability in the routing protocol daemon (RPD) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated adjacent attacker to cause high load on RPD which in turn may lead to routing protocol flaps. If a system with sensor-based-stats enabled receives a specific LDP FEC this can lead to the above condition. Continued receipted of such an LDP FEC will create a sustained Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS 19.2 version 19.2R2 and later versions prior to 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S2; 19.4 versions prior to 19.4R1-S4, 19.4R2-S4, 19.4R3-S2; 20.1 versions prior to 20.1R2-S1, 20.1R3; 20.2 versions prior to 20.2R2-S1, 20.2R3; 20.3 versions prior to 20.3R1-S2, 20.3R2. This issue does not affect Juniper Networks Junos OS versions prior to 19.2R2. Juniper Networks Junos OS Evolved All versions prior to 20.1R2-S3-EVO; 20.3 versions prior to 20.3R1-S2-EVO.

Remediation

Solution:

  • The following software releases have been updated to resolve this specific issue in Junos OS: 19.2R3-S3, 19.3R2-S6, 19.3R3-S2, 19.4R1-S4, 19.4R2-S4, 19.4R3-S2, 20.1R2-S1, 20.1R3, 20.2R2-S1, 20.2R3, 20.3R1-S2, 20.3R2, 20.4R1, and all subsequent releases. The following software releases have been updated to resolve this specific issue in Junos OS Evolved: 20.1R2-S3-EVO, 20.3R1-S2-EVO, 20.4R1-EVO, and all subsequent releases.

Workaround:

  • For Junos OS turn off sensor-based-stats by deleting: [protocols ldp traffic-statistics sensor-based-stats] For Junos OS Evolved mLDP will have to be turned off as sensor-based-stats is the default: [protocols ldp p2mp]

Category

6.5
CVSS
Severity: Medium
CVSS 3.1 •
CVSS 2.0 •
EPSS 0.08%
Vendor Advisory juniper.net
Affected: Juniper Networks Junos OS
Affected: Juniper Networks Junos OS Evolved
Published at:
Updated at:

References

Link Tags
https://kb.juniper.net/JSA11225 patch vendor advisory

Frequently Asked Questions

What is the severity of CVE-2021-31363?
CVE-2021-31363 has been scored as a medium severity vulnerability.
How to fix CVE-2021-31363?
To fix CVE-2021-31363: The following software releases have been updated to resolve this specific issue in Junos OS: 19.2R3-S3, 19.3R2-S6, 19.3R3-S2, 19.4R1-S4, 19.4R2-S4, 19.4R3-S2, 20.1R2-S1, 20.1R3, 20.2R2-S1, 20.2R3, 20.3R1-S2, 20.3R2, 20.4R1, and all subsequent releases. The following software releases have been updated to resolve this specific issue in Junos OS Evolved: 20.1R2-S3-EVO, 20.3R1-S2-EVO, 20.4R1-EVO, and all subsequent releases.
Is CVE-2021-31363 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2021-31363 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-31363?
CVE-2021-31363 affects Juniper Networks Junos OS, Juniper Networks Junos OS Evolved.
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