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Junos Os EvolvedOperating system · Juniper

CVE-2021-0297

MEDIUM · 6.5 CVSS v3.1 Published 2021-10-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable 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
A vulnerability in the processing of TCP MD5 authentication in Juniper Networks Junos OS Evolved may allow a BGP or LDP session configured with MD5 authentication to succeed, even if the peer does not have TCP MD5 authentication enabled. This could lead to untrusted or unauthorized sessions being established, resulting in an impact on confidentiality or stability of the network. This issue affects Juniper Networks Junos OS Evolved: All versions prior to 20.3R2-S1-EVO; 20.4 versions prior to 20.4R2-EVO; 21.1 versions prior to 21.1R2-EVO. Juniper Networks Junos OS is not affected by this issue.

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

A TCP MD5 authentication bypass vulnerability in Juniper Networks Junos OS Evolved allows BGP or LDP sessions with MD5 authentication to be established even when the peer does not have TCP MD5 authentication enabled, potentially allowing unauthorized or untrusted sessions to form.

MitigationUpgrade Junos OS Evolved to version 20.3R2-S1-EVO, 20.4R2-EVO, 21.1R2-EVO or later. Verify that MD5 authentication is properly configured and enforced on both peers of all BGP and LDP sessions.

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
Junos Os EvolvedOperating system
Affected:= 20.3= 20.4= 21.1

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

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

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. Check Junos OS Evolved version
    Run 'show version' or 'system version' to obtain the installed Junos OS Evolved version
    Affected if Version is exactly 20.3, 20.4, or 21.1
  2. Verify BGP MD5 authentication configuration
    Run 'show configuration protocols bgp group <group-name> | display set' to view BGP group MD5 authentication settings
    Affected if TCP MD5 authentication is configured on any BGP group or neighbor and the device version matches the affected versions above
  3. Verify LDP MD5 authentication configuration
    Run 'show configuration protocols ldp | display set' to view LDP interface MD5 authentication settings
    Affected if TCP MD5 authentication is configured on any LDP interface and the device version matches the affected versions above
  4. Inspect active BGP session status
    Run 'show bgp neighbor' and check for established sessions, noting the authentication method in use
    Affected if BGP sessions are established and the version is affected, regardless of whether MD5 is showing as configured on both ends
  5. Inspect active LDP session status
    Run 'show ldp neighbor' to view established LDP sessions and their authentication status
    Affected if LDP sessions are established and the version is affected

The environment is affected if Junos OS Evolved is running version 20.3, 20.4, or 21.1 AND BGP or LDP sessions with TCP MD5 authentication are configured.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Junos OS Evolved to version 20.3R2-S1-EVO, 20.4R2-EVO, 21.1R2-EVO or later. Verify that MD5 authentication is properly configured and enforced on both peers of all BGP and LDP sessions.

Recommended fix High confidence

Upgrade to 20.3R2-S1-EVO, 20.4R2-EVO, or 21.1R2-EVO (or subsequent releases) depending on your current version branch

  1. Identify the current Junos OS Evolved version using the 'show version' command
  2. Schedule a maintenance window for the upgrade procedure
  3. Download the appropriate fixed version from the Juniper Networks support portal: 20.3R2-S1-EVO or later for 20.3 branch, 20.4R2-EVO or later for 20.4 branch, or 21.1R2-EVO or later for 21.1 branch
  4. Upload the software package to the device using standard file transfer methods
  5. Execute the Junos OS Evolved upgrade command (request system software add <package-name>)
  6. Reboot the device as prompted by the upgrade process
  7. After reboot, verify the new version is installed using 'show version'
  8. Test BGP and LDP sessions with MD5 authentication to confirm the vulnerability is remediated - sessions should now fail if the peer does not have matching MD5 authentication configured
Caveat Review Junos OS Evolved release notes for any behavioral changes between your current version and the target fixed version before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Junos Os Evolved Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2021-0297 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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