Security readout for executives and security teams
Plain-English summary
Certain Juniper routers, switches, and security gateways can have Ethernet interfaces forced down by specially crafted frames from the same local Ethernet segment. The affected interface does not recover automatically, so availability can remain impaired until the FPC is manually reset.
Executive priority
Treat this as a targeted availability risk for critical Juniper network infrastructure, not a broad remote compromise issue. Prioritize remediation where affected interfaces support core, edge, data-center, or security traffic paths.
Technical view
CVE-2021-0290 is a Junos OS CWE-755 condition in Ethernet frame processing. On specified MX, EX9200/EX9251, and SRX4600 platforms or line cards, adjacent unauthenticated traffic can trigger a persistent interface-down state, causing denial of service. CVSS is 6.5 with adjacent-network attack vector and high availability impact.
Likely exposure
Exposure is limited to the affected Junos OS versions and listed Juniper platforms or line cards. The attacker must be on the local Ethernet segment, so internet-wide remote exposure is not indicated by the sources.
Exploitation context
The provided sources do not show active exploitation, and the CVE is not marked KEV. The practical risk is localized denial of service against critical network interfaces where an adjacent Layer 2 attacker can send malformed frames.
Researcher notes
The advisory states no products or platforms outside the named list are affected. Evidence supports adjacent-network DoS only, with no confidentiality or integrity impact and no source-backed active exploitation claim.
Mitigation direction
- Upgrade affected Junos OS to Juniper's fixed releases listed in JSA11192.
- Prioritize MX, EX9200/EX9251, and SRX4600 devices on critical network paths.
- Restrict untrusted Layer 2 adjacency to affected interfaces where operationally feasible.
- Monitor for DFE tuning failures and permanently down Ethernet links.
- Follow Juniper guidance for recovery, including FPC reset handling.
Validation and detection
- Inventory Junos OS versions and compare them with Juniper's affected ranges.
- Verify platform and line-card combinations match Juniper's affected list.
- Review logs for "Failed to complete DFE tuning" messages.
- Check interfaces that are administratively up but unexpectedly link down.
- Avoid marking unrelated Juniper products vulnerable unless Juniper lists them.
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.
CWE-755: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-0290 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/JSA11192CVE 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 Handling of Exceptional Conditions
Improper Handling of Exceptional Conditions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.