Security readout for executives and security teams
Plain-English summary
This Junos OS flaw can let a network attacker bypass storm-control during a rare race condition, potentially causing denial of service. It is more likely on Virtual Chassis deployments and depends on specific administrator actions occurring at the wrong time. Treat it as high priority for exposed Juniper estates, but not as confirmed actively exploited.
Executive priority
High. This is an availability risk in network infrastructure, with stronger urgency where affected Junos devices protect critical switching or edge paths. Patch planning should be prioritized, especially for Virtual Chassis deployments, while noting that public active exploitation is not evidenced in the provided sources.
Technical view
CVE-2021-0244 is a signal-handler race condition in Junos OS Layer 2 Address Learning Daemon. Missing race-condition protection may allow storm-control bypass and availability impact. The issue is a corner case, triggered under specific administrator actions, with higher event frequency in Virtual Chassis configurations.
Likely exposure
Exposure is limited to Juniper Networks Junos OS versions listed in the advisory, especially environments using storm-control and Virtual Chassis. Affected trains include 14.1X53, 15.1, 15.1X49, 16.x, 17.x, 18.x, and 19.1 before specified fixed releases.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. CVSS indicates network attackability, no privileges, and high availability impact, but user interaction is required and the vulnerable condition depends on specific administrative activity.
Researcher notes
Key nuance: the vulnerability is not described as platform-specific, but affected release notes call out EX for 14.1X53 and SRX for 15.1X49. The source provides an IoC log message and fixed release thresholds, but no CWE, exploit proof, or separate workaround.
Mitigation direction
- Upgrade Junos OS to the fixed release for the deployed version train.
- Prioritize Virtual Chassis systems and devices using storm-control profiles.
- Review Juniper JSA11137 for platform-specific fixed releases and operational guidance.
- Monitor logs for the documented storm-control blob failure message.
- Avoid assuming compensating controls fully remove risk without vendor confirmation.
Validation and detection
- Inventory Junos OS versions across Juniper devices.
- Identify devices configured with storm-control profiles.
- Identify Virtual Chassis deployments for priority review.
- Review system logs for the documented storm-control failure indicator.
- Confirm upgraded devices are on or beyond the fixed release listed by Juniper.
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-2021-0244 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
- High
- CVSS
- 7.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/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:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:H2.84Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.4HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11137CVE 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.