Security readout for executives and security teams
Plain-English summary
This vulnerability can make certain Juniper switch clusters repeatedly crash a forwarding process, disrupting network availability. It only applies to listed EX and QFX platforms running affected Junos OS releases in Virtual Chassis mode with a specific Layer 2 circuit configuration.
Executive priority
Treat as a targeted network availability risk for affected Juniper switching clusters. Prioritize remediation where these devices support critical campus, data center, or service-provider Layer 2 connectivity.
Technical view
CVE-2021-0237 is an adjacent-network, unauthenticated denial-of-service issue in Junos OS. Specific Layer 2 frames can crash and restart the FXPC process on affected EX4300-MP, EX4600, EX4650, and QFX5K Virtual Chassis deployments, potentially causing sustained DoS if packets continue.
Likely exposure
Exposure appears narrower than internet-facing software: affected Juniper EX/QFX devices must be in Virtual Chassis mode, on vulnerable Junos OS versions, and using the relevant Layer 2 circuit configuration.
Exploitation context
The bundle does not show CISA KEV listing or other evidence of active exploitation. CVSS indicates adjacent network access, low complexity, no privileges, no user interaction, and high availability impact.
Researcher notes
No CWE is provided in the bundle. The key constraints are platform family, Virtual Chassis deployment, Junos release train, and specific Layer 2 circuit configuration. Avoid broad product assumptions beyond the named EX4300-MP, EX4600, EX4650, and QFX5K Series.
Mitigation direction
- Identify listed Juniper platforms running affected Junos OS versions in Virtual Chassis mode.
- Upgrade affected systems to Junos releases at or beyond the fixed versions listed by Juniper.
- Review Juniper JSA11132 for platform-specific guidance before scheduling changes.
- Monitor FXPC restarts and availability symptoms until remediation is complete.
Validation and detection
- Confirm device model, Virtual Chassis status, Junos version, and Layer 2 circuit configuration.
- Compare installed releases with affected version ranges in CVE-2021-0237 and JSA11132.
- Review logs or telemetry for FXPC crashes or restarts tied to Layer 2 traffic.
- After upgrade, verify FXPC stability during normal Layer 2 operations.
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
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2021-0237 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11132CVE reference · x_refsource_MISC
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.