Security readout for executives and security teams
Plain-English summary
Certain Juniper Junos OS routers using BGP origin validation with RPKI may incorrectly accept or pass along a spoofed route advertisement. For network operators, this can weaken route-validation controls intended to prevent routing mistakes or abuse.
Executive priority
Treat as high priority for organizations relying on Juniper BGP routers and RPKI to protect routing integrity. The issue can undermine a key control against spoofed route advertisements, especially at network edges.
Technical view
CVE-2021-31375 is improper input validation in Junos OS RPD. A specific BGP update can bypass RPKI policy checks on affected Junos versions configured for BGP origin validation, potentially allowing spoofed advertisements to be accepted or propagated.
Likely exposure
Exposure is limited to Juniper Networks Junos OS devices on affected release trains that are configured with BGP origin validation using RPKI. Devices not using that feature are not described as exposed by the provided sources.
Exploitation context
The source bundle does not show CISA KEV listing or other evidence of active exploitation. The attack is network-reachable and unauthenticated in CVSS, but requires sending a specific BGP update to a susceptible routing context.
Researcher notes
Affected versions include Junos OS 12.3, 15.1, 17.2 through 19.3 before specified fixed releases. Evidence supports input-validation failure in RPD affecting RPKI policy enforcement; exploit details are not provided in the bundle.
Mitigation direction
- Identify affected Junos OS release trains in routing infrastructure.
- Upgrade to Juniper fixed releases or later, per JSA11240.
- Prioritize internet-facing or peering-edge BGP routers using RPKI origin validation.
- Review Juniper advisory for any environment-specific guidance.
- Monitor route validation and propagation anomalies during remediation.
Validation and detection
- Inventory Junos OS versions on BGP routers.
- Confirm whether BGP origin validation with RPKI is enabled.
- Compare installed versions against affected ranges in the advisory.
- Review routing logs for unexpected accepted or propagated invalid routes.
- Confirm upgraded devices run fixed or later Junos OS builds.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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Open ATT&CK lookupCWE-358: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-31375 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.2 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:L3.92.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.2HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11240CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improperly Implemented Security Check for Standard
Improperly Implemented Security Check for Standard represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.