Security readout for executives and security teams
Plain-English summary
This is a service availability risk in specific Juniper MX and EX9200 routing platforms. Certain customer-edge Layer 2 events can leak memory on Trio-based line cards when IRB is tied to VPLS or a bridge-domain. If memory is exhausted, the MPC can restart, causing temporary traffic interruption.
Executive priority
Treat as a moderate operational risk where affected Juniper PE routers support important customer services. It is not described as data theft or privilege compromise, but an MPC restart can interrupt traffic. Prioritize remediation for high-value network segments and heavily used VPLS environments.
Technical view
Affected Junos OS releases on MX Series and EX9200 Series with Trio-based MPC/PFEs can leak next-hop memory under specific IRB plus VPLS or bridge-domain configurations. The issue is CWE-400 resource consumption, CVSS 6.5, adjacent-network, no authentication required, with high availability impact and no confidentiality or integrity impact.
Likely exposure
Exposure is limited to Juniper MX Series and EX9200 Series using listed Trio-based MPCs/PFEs with IRB interfaces mapped to VPLS instances or bridge-domains on affected Junos OS versions. The vendor states no other products or platforms are affected.
Exploitation context
The source bundle does not cite active exploitation, and the CVE is not marked KEV. Triggering requires relevant Layer 2 network events at customer-edge devices and adjacency to the affected network context, so this is mainly an outage and resilience concern for provider-edge environments.
Researcher notes
The advisory scope is narrow: Trio-based MPC/PFE platforms, IRB mapped to VPLS or bridge-domain, and specified Junos trains. The observable failure mode is next-hop memory depletion followed by MPC restart. Evidence provided does not establish public exploitation or broader platform impact.
Mitigation direction
- Upgrade affected Junos OS trains to Juniper's listed fixed releases or later.
- Prioritize PE devices carrying critical VPLS or bridge-domain services.
- Review Juniper JSA11148 for exact fixed releases and operational guidance.
- Monitor affected MPC memory until remediation is complete.
- Plan maintenance windows for upgrades because PE line-card restarts affect traffic.
Validation and detection
- Inventory MX and EX9200 devices with Trio-based MPCs or PFEs.
- Identify IRB interfaces mapped to VPLS instances or bridge-domains.
- Compare Junos OS versions against the affected and fixed release ranges.
- Monitor FPC resource output for declining % NH mem Free.
- Review device history for MPC restarts and related traffic interruptions.
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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CWE-400: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-0257 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/JSA11148CVE 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.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.