CVE-2021-31382

What it is

On PTX1000 System, PTX10002-60C System, after upgrading to an affected release, a Race Condition vulnerability between the chassis daemon (chassisd) and firewall process (dfwd) of Juniper Networks Junos OS, may update the device's interfaces with incorrect firewall filters. This issue only occurs when upgrading the device to an affected version of Junos OS. Interfaces intended to have protections may have no protections assigned to them. Interfaces with one type of protection pattern may have alternate protections assigned to them. Interfaces intended to have no protections may have protections assigned to them. These firewall rule misassignments may allow genuine traffic intended to be stopped at the interface to propagate further, potentially causing disruptions in services by propagating unwanted traffic. An attacker may be able to take advantage of these misassignments. This issue affects Juniper Networks Junos OS on PTX1000 System: 17.2 versions 17.2R1 and later versions prior to 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R1-S8, 18.4R2-S8, 18.4R3-S8; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R3-S2; 19.3 versions prior to 19.3R2-S6, 19.3R3-S3; 19.4 versions prior to 19.4R2-S4, 19.4R3-S3; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R2-S3, 20.2R3; 20.3 versions prior to 20.3R2-S1, 20.3R3; 20.4 versions prior to 20.4R1-S1, 20.4R2. This issue does not affect Juniper Networks Junos OS prior to version 17.2R1 on PTX1000 System. This issue affects Juniper Networks Junos OS on PTX10002-60C System: 18.2 versions 18.2R1 and later versions prior to 18.4 versions prior to 18.4R3-S9; 19.1 versions later than 19.1R1 prior to 19.4 versions prior to 19.4R2-S5, 19.4R3-S5; 20.1 versions prior to 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3-S1; 20.4 versions 20.4R1 and later versions prior to 21.1 versions prior to 21.1R2; 21.2 versions 21.2R1 and later versions prior to 21.3 versions prior to 21.3R2. This issue does not affect Juniper Networks Junos OS prior to version 18.2R1 on PTX10002-60C System. This issue impacts all filter families (inet, inet6, etc.) and all loopback filters. It does not rely upon the location where a filter is set, impacting both logical and physical interfaces.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.6% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-10-19 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:51 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.6% in the next 30 days (EPSS).
• Severity: 6.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-10-19 19:15 UTC

Last modified

2026-06-17 03:51 UTC

Exploit probability

0.6% · EPSS, next 30 days

Weakness

CWE-362 · Race condition

Record status

Modified

Affected

• Juniper Junos 17.2
• Juniper Junos 17.2x75
• Juniper Junos 17.3
• Juniper Junos 17.4
• Juniper Junos 18.1
• Juniper Junos 18.2
• Juniper Junos 18.3
• Juniper Junos 18.4

Attack profile CVSS 3.1 · 6.5

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-31382.md and follow it. Check whether this project is affected by CVE-2021-31382. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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