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JunosOperating system · Juniper

CVE-2021-31375

MEDIUM · 5.3 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 →
62/100
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
An Improper Input Validation vulnerability in routing process daemon (RPD) of Juniper Networks Junos OS devices configured with BGP origin validation using Resource Public Key Infrastructure (RPKI), allows an attacker to send a specific BGP update which may cause RPKI policy-checks to be bypassed. This, in turn, may allow a spoofed advertisement to be accepted or propagated. This issue affects: Juniper Networks Junos OS 12.3 versions prior to 12.3R12-S18; 15.1 versions prior to 15.1R7-S9; 17.2 versions prior to 17.2R3-S3; 17.3 versions prior to 17.3R3-S7; 17.4 versions prior to 17.4R2-S9, 17.4R3; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S3; 18.3 versions prior to 18.3R3-S1; 18.4 versions prior to 18.4R3; 19.1 versions prior to 19.1R2; 19.2 versions prior to 19.2R2; 19.3 versions prior to 19.3R2.

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 input validation in Junos OS RPD allows attackers to bypass BGP origin validation when RPKI is configured. By sending specially crafted BGP updates, an attacker can cause RPKI policy-checks to be circumvented, enabling spoofed route advertisements to be accepted and propagated throughout the BGP domain.

MitigationUpgrade Junos OS to the fixed versions specified in the vendor advisory (12.3R12-S18, 15.1R7-S9, 17.2R3-S3, 17.3R3-S7, 17.4R2-S9, 17.4R3, 18.1R3-S13, 18.2R3-S3, 18.3R3-S1, 18.4R3, 19.1R2, 19.2R2, or 19.3R2 or later). If immediate upgrade is not feasible, consider disabling BGP origin validation or implementing additional BGP route filtering as a compensating control.

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:= 12.3= 15.1= 17.2= 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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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 installed Junos OS version
    Execute `show version` on the device CLI to retrieve the exact Junos version installed
    Affected if The version matches any of these: 12.3, 15.1, 17.2, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, or 19.3 (any subversion) - these are the affected versions listed in the CVE
  2. Verify RPKI is configured
    Execute `show configuration | display json | match rpki` or inspect the BGP configuration with `show configuration protocols bgp` to see if RPKI (origin validation) is defined
    Affected if RPKI configuration lines are present under the BGP protocol stanza, meaning RPKI-based origin validation is enabled on the device
  3. Confirm RPKI connections are active
    Execute `show rpki connections` to check if the device has active RPKI validator sessions
    Affected if The output shows active connections to RPKI validators, confirming RPKI is actively in use for BGP route validation
  4. Check BGP origin validation policy
    Execute `show policy` or `show configuration policy-options` to review any BGP origin-validation policies applied
    Affected if Origin validation policies are applied to BGP peer groups or routing instances, meaning RPKI validation results are being used to filter routes

The device is affected if it runs any Junos version listed as affected AND has RPKI (BGP origin validation) configured and actively used, because the vulnerability specifically bypasses RPKI validation checks.

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 to the fixed versions specified in the vendor advisory (12.3R12-S18, 15.1R7-S9, 17.2R3-S3, 17.3R3-S7, 17.4R2-S9, 17.4R3, 18.1R3-S13, 18.2R3-S3, 18.3R3-S1, 18.4R3, 19.1R2, 19.2R2, or 19.3R2 or later). If immediate upgrade is not feasible, consider disabling BGP origin validation or implementing additional BGP route filtering as a compensating control.

Recommended fix High confidence

12.3 to 12.3R12-S18; 15.1 to 15.1R7-S9; 17.2 to 17.2R3-S3; 17.3 to 17.3R3-S7; 17.4 to 17.4R2-S9 or 17.4R3; 18.1 to 18.1R3-S13; 18.2 to 18.2R3-S3; 18.3 to 18.3R3-S1; 18.4 to 18.4R3; 19.1 to 19.1R2; 19.2 to 19.2R2; 19.3 to 19.3R2

  1. 1. Identify the current Junos OS version by running 'show version' on the device
  2. 2. Identify which affected version branch your device is running (12.3, 15.1, 17.2, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, or 19.3)
  3. 3. Determine the appropriate fixed release for your version branch from the upgrade path list
  4. 4. Download the recommended Junos Service Release (SPR) or main release from the Juniper Networks support portal
  5. 5. Upload the Junos upgrade package to the device using 'file copy' or USB transfer
  6. 6. Perform a system upgrade using 'request system software add <package>' command
  7. 7. After upgrade completes, reboot the device using 'request system reboot'
  8. 8. After reboot, verify the new version is running with 'show version'
Caveat Review Juniper Networks release notes for each target version for any configuration or feature changes; some older hardware platforms may have limited upgrade paths

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

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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

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Peer-ranked notes from engineers who’ve handled CVE-2021-31375 in production — separate from our analysis above.

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