Security readout for executives and security teams
Plain-English summary
This is an availability risk for specific Juniper MX broadband gateways using IPv6 NDP proxy with EVPN leaf nodes. Specially crafted IPv6 neighbor discovery traffic can cause stale MAC entries, making legitimate traffic get dropped. It does not affect IPv4 ARP proxy or Junos releases before 17.4.
Executive priority
Treat this as high priority for service-provider or enterprise edge networks using Juniper MX BNG with IPv6. The business risk is service disruption, not data theft. If the affected feature is absent, urgency drops substantially.
Technical view
CVE-2020-1633 is a CWE-20 input validation flaw in Junos OS on MX Series BNG deployments using the IPv6 NDP proxy feature introduced in 17.4. Crafted NDPv6 packets can transit the BNG to an EVPN leaf node, create stale MAC state, and cause denial of service through traffic discard.
Likely exposure
Exposure is limited to Juniper MX Series running affected Junos OS 17.4 through 19.2 trains, configured as a BNG with IPv6 NDP proxy. IPv4 ARP proxy is unaffected, and pre-17.4 releases are not affected because they lack the feature.
Exploitation context
The CVSS vector indicates adjacent-network reachability, low attack complexity, no privileges, and no user interaction, with high availability impact. The provided sources do not state active exploitation, and the CVE is not marked as CISA KEV.
Researcher notes
The issue is narrow but operationally significant. Key scoping facts are IPv6-only impact, MX Series BNG role, Junos 17.4 and later affected trains, and stale MAC state leading to discarded legitimate traffic. Sources do not provide exploit proof-of-concept details or evidence of in-the-wild exploitation.
Mitigation direction
- Upgrade affected Junos OS trains to the fixed versions listed by Juniper.
- Prioritize MX Series devices serving BNG roles with IPv6 NDP proxy enabled.
- Confirm IPv4-only ARP proxy deployments are not incorrectly included in remediation scope.
- Check Juniper advisory JSA11012 for current vendor guidance before maintenance.
- Use normal change controls because remediation affects routing infrastructure.
Validation and detection
- Inventory MX Series devices and record Junos OS release trains and exact versions.
- Identify BNG configurations using IPv6 NDP proxy and EVPN leaf node paths.
- Compare versions against Juniper's fixed release thresholds for each train.
- Review network symptoms for unexplained IPv6 traffic drops or stale MAC behavior.
- Confirm remediation by verifying upgraded Junos versions after maintenance.
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-20: Exact CWE lookup
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Open ATT&CK lookupCVE-2020-1633 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:A/AC:L/PR:N/UI:N/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:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H2.84Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.4HighVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://kb.juniper.net/JSA11012CVE 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 Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.