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JunosOperating system · Juniper

CVE-2021-0290

MEDIUM · 6.5 CVSS v3.1 Published 2021-07-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
Remediation priority · Elevated
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Improper handling of exceptional conditions in Ethernet interface frame processing in Juniper Networks Junos OS allows an attacker on the local Ethernet segment to send specially crafted frames that cause the interface to enter a permanently down state, requiring manual FPC reset. The issue affects MPC7E/8E/9E and MPC10E line cards on specific MX Series routers, EX9200/EX9251 switches, and SRX4600 firewalls.

MitigationApply the appropriate Junos OS software patch for affected versions (16.1R7-S7, 17.2R3-S3, 17.3R3-S8, 17.4R2-S11/17.4R3-S1, 18.1R3-S10, 18.2R3-S3, 18.3R3-S1, 18.4R2-S3/18.4R3, 19.1R2-S1/19.1R3, 19.2R1-S3/19.2R2, or 19.3R2 and later). Monitor for 'Failed to complete DFE tuning' syslog messages indicating exploitation attempts.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
JunosOperating system
Affected:= 16.1= 17.1= 17.3= 17.4= 18.1= 18.2= 18.3= 18.4= 19.1= 19.2= 19.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify Junos OS version is affected
    Run 'show version' or 'show version detail' to identify the installed Junos version
    Affected if Version is 16.1, 17.1, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, or 19.3 (any release within these branches)
  2. Confirm affected hardware line card is present
    Run 'show chassis fpc' or 'show hardware' to list installed line cards
    Affected if MPC7E, MPC8E, MPC9E, or MPC10E line cards are present in the system
  3. Verify platform is an affected model
    Run 'show chassis hardware' or check model via 'show system information'
    Affected if Device is an MX Series router, EX9200 switch, EX9251 switch, or SRX4600 firewall
  4. Check for exploitation indicators
    Search syslog for 'Failed to complete DFE tuning' messages, and run 'show interfaces' to verify any Ethernet interfaces are in down state unexpectedly
    Affected if Syslog contains DFE tuning failure messages or interfaces on affected line cards are persistently down without manual reset

User is affected if running a vulnerable Junos version on an MX Series, EX9200/EX9251, or SRX4600 platform with MPC7E/8E/9E/10E line cards, especially if DFE tuning failures appear in logs or interfaces are down.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the appropriate Junos OS software patch for affected versions (16.1R7-S7, 17.2R3-S3, 17.3R3-S8, 17.4R2-S11/17.4R3-S1, 18.1R3-S10, 18.2R3-S3, 18.3R3-S1, 18.4R2-S3/18.4R3, 19.1R2-S1/19.1R3, 19.2R1-S3/19.2R2, or 19.3R2 and later). Monitor for 'Failed to complete DFE tuning' syslog messages indicating exploitation attempts.

Fix this in Junos Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-0290 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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