Security readout for executives and security teams
Plain-English summary
CVE-2021-0273 can make certain Juniper routing and switching platforms suffer a denial of service when affected logical-tunnel interfaces process specific traffic. The issue is availability-only, but it matters for organizations using listed Trio-based line cards in core or edge network roles.
Executive priority
Treat this as a moderate operational resilience issue. It is not a data theft or integrity risk, but it can affect network availability where vulnerable Juniper hardware and LT-LT interfaces are deployed in important paths.
Technical view
Affected Junos OS and Junos OS Evolved releases on specific ACX5800, EX9200, MX10000, MX240, MX480, and MX960 devices can loop packets in Trio PFE microcode for LT-LT interfaces. The flaw is tied to incorrect control flow in implicit filter terms and can sustain high LT interface traffic until interrupted.
Likely exposure
Exposure is limited to listed Juniper platforms, affected Trio line cards, vulnerable Junos versions, and LT-LT interfaces. MX10001 is explicitly excluded, and other interface types are not affected according to the source bundle.
Exploitation context
The CVSS vector is network-accessible with low complexity and no privileges or user interaction. The bundle does not indicate CISA KEV listing or active exploitation, so exploitation should not be stated as observed.
Researcher notes
Key constraints are important: the issue affects only LT-LT interfaces and named Trio line cards on specified Junos trains. The source provides an operational indicator based on excessive LT interface traffic, but does not provide evidence of exploitation in the wild.
Mitigation direction
- Upgrade to a Juniper release outside the affected version ranges.
- Check Juniper JSA11164 for current platform-specific remediation guidance.
- If the loop occurs, disable one side of the affected LT interface to clear it.
- Re-enable the disabled LT interface only after the condition has cleared.
- Prioritize devices carrying critical routing, peering, or internal segmentation traffic.
Validation and detection
- Inventory affected Juniper platforms and Trio line cards.
- Check Junos OS and Junos OS Evolved versions against listed vulnerable ranges.
- Identify configured LT-LT interfaces on in-scope devices.
- Monitor LT-LT traffic for abnormal sustained high utilization.
- Confirm MX10001 and non-LT interfaces are excluded from scope.
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
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CWE-670: Exact CWE lookup
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Open ATT&CK lookupCWE-835: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-0273 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
- 5.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:U/C:N/I:N/A:L3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11164CVE 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.
Always-Incorrect Control Flow Implementation
Always-Incorrect Control Flow Implementation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Loop with Unreachable Exit Condition ('Infinite Loop')
Loop with Unreachable Exit Condition ('Infinite Loop') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.