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CVE Record

CVE-2021-0235: Junos OS: SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3, vSRX Series: In a multi-tenant environment, a tenant host administrator may configure logical firewall isolation affecting other tenant networks

On SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3, vSRX Series devices using tenant services on Juniper Networks Junos OS, due to incorrect permission scheme assigned to tenant system administrators, a tenant system administrator may inadvertently send their network traffic to one or more tenants while concurrently modifying the overall device system traffic management, affecting all tenants and the service provider. Further, a tenant may inadvertently receive traffic from another tenant. This issue affects: Juniper Networks Junos OS 18.3 version 18.3R1 and later versions on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2; 18.4 version 18.4R1 and later versions on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3; 19.1 versions 19.1R1 and later versions on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3; 19.2 versions prior to 19.2R1-S6, 19.2R3-S2 on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3; 19.3 versions prior to 19.3R3-S2 on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3; 19.4 versions prior to 19.4R2-S4, 19.4R3-S2 on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3; 20.1 versions prior to 20.1R2, 20.1R3 on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3 vSRX Series; 20.2 versions prior to 20.2R2-S1, 20.2R3 on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3 vSRX Series; 20.3 versions prior to 20.3R1-S2, 20.3R2 on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3 vSRX Series; 20.4 versions prior to 20.4R1, 20.4R2 on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 Series with SPC2/SPC3 vSRX Series. This issue does not affect Juniper Networks Junos OS versions prior to 18.3R1.

HighCVSS 7.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A privileged tenant administrator on affected Juniper SRX or vSRX multi-tenant deployments could change traffic management in ways that break tenant isolation. The business impact is cross-tenant traffic exposure or disruption, especially for service providers hosting multiple customer networks on shared firewall infrastructure.

Executive priority

Treat as high priority where Juniper firewalls host multiple tenants or customers. The issue is not broadly remote, but it undermines tenant isolation, which can create confidentiality, integrity, and availability consequences across customer environments.

Technical view

CVE-2021-0235 is an incorrect permission scheme issue in Junos OS tenant services on specified SRX and vSRX platforms. With local access and high privileges, a tenant system administrator may affect logical firewall isolation, causing traffic to be sent to or received from other tenants. CVSS 3.1 is 7.3 with changed scope.

Likely exposure

Exposure is limited to affected Junos OS versions on SRX1500, SRX4100, SRX4200, SRX4600, SRX5000 with SPC2/SPC3, and vSRX Series using tenant services in multi-tenant environments.

Exploitation context

The provided sources do not show active exploitation, and the CVE is not listed as KEV. Exploitation requires local access and high privileges as a tenant system administrator, but successful misuse can affect other tenants and the provider environment.

Researcher notes

Key constraints are AV:L and PR:H, so validation should focus on tenant-admin role boundaries, logical firewall isolation, and affected release mapping. The source bundle does not provide exploit evidence or detailed workaround text beyond vendor advisory reference and affected fixed-version thresholds.

Mitigation direction

  • Review Juniper JSA11130 for the authoritative fixed release guidance.
  • Upgrade affected Junos OS branches to a non-affected fixed version.
  • Prioritize shared service-provider and customer-hosting firewall environments.
  • Restrict and review tenant administrator privileges until upgrades are complete.
  • Audit tenant-service configuration changes for unintended cross-tenant impact.

Validation and detection

  • Inventory SRX and vSRX systems using Junos OS tenant services.
  • Compare deployed Junos OS versions against the affected version ranges.
  • Confirm hardware includes listed SRX platforms with SPC2/SPC3 or vSRX Series.
  • Review tenant firewall isolation policies for unintended shared traffic paths.
  • Check administrative logs for tenant-level traffic-management changes.
Prepared
Confidence
high
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-276: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-0235 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.3 (3.1)
Known Exploited
No
Published

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

Official CVE source material

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.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We 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.

ScoreVersionSeverityVectorExploitImpactSource
7.3CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:L/I:H/A:L1.55.3Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.3High
CVSS 3.1 vector shape for CVE-2021-0235Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Juniper NetworksJunos OS18.3R1Listed
Juniper NetworksJunos OS18.4R1, 19.1R1, 19.2, 19.3, 19.4Listed
Juniper NetworksJunos OS20.1, 20.2, 20.3, 20.4Listed
Juniper NetworksJunos OSunspecifiedListed
Weakness

CWE details

CWE-276

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-276 · source CWE mapping

Incorrect Default Permissions

Incorrect Default Permissions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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