Security readout for executives and security teams
Plain-English summary
CVE-2021-0224 can make affected Juniper Junos OS systems repeatedly crash the ANCP daemon when too many broadband subscriber nodes are processed. For providers using Layer 2 BRAS subscriber infrastructure, this is an availability risk, not a data theft issue.
Executive priority
Address during normal vulnerability remediation cycles, with faster handling for subscriber edge networks where ANCPD instability could disrupt broadband access services. This is not presented as actively exploited, but it can affect availability.
Technical view
In Junos OS ANCPD, exceeding the configured maximum-discovery-table-entries limit can leave a subscriber unmapped to an internal neighbor entry, causing ANCPD to crash and restart. Continued spoofed subscriber-node processing can sustain denial of service. CVSS is 6.5, adjacent network, no privileges, availability impact high.
Likely exposure
Exposure is most likely in Juniper Junos OS deployments using ANCPD for Layer 2 BRAS subscriber node discovery. The CVE lists multiple affected Junos OS release trains before specified fixed releases through 20.3R2.
Exploitation context
The source bundle does not identify active exploitation, and KEV status is false. The described abuse requires adjacent-network access and enough spoofed or excessive subscriber-node discovery activity to exceed the configured discovery table limit.
Researcher notes
This is CWE-770, improper resource control. The available evidence supports a denial-of-service condition in ANCPD tied to subscriber discovery table exhaustion. No exploit code, active exploitation, or workaround details are provided in the source bundle beyond fixed release guidance.
Mitigation direction
- Upgrade affected Junos OS releases to the fixed versions listed for each release train.
- Review Juniper JSA11119 for authoritative remediation and any platform-specific guidance.
- Prioritize BRAS or ANCPD-enabled subscriber edge systems over unrelated Junos devices.
- Treat repeated ANCPD restarts as service-impacting until fixed or otherwise mitigated.
Validation and detection
- Inventory Junos OS versions and compare them with the affected release ranges.
- Identify systems using ANCPD, Layer 2 BRAS, or subscriber node discovery features.
- Review operational logs for ANCPD crash, core, or restart events.
- Check whether subscriber discovery attempts approach maximum-discovery-table-entries limits.
- Confirm remediation by verifying the installed Junos OS release is at or above the fixed version.
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-770: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-0224 mapping review
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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/JSA11119CVE 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.
Allocation of Resources Without Limits or Throttling
Allocation of Resources Without Limits or Throttling represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.