Security readout for executives and security teams
Plain-English summary
Cisco Intersight Virtual Appliance can incorrectly forward IPv4 or IPv6 traffic from its external management interface to sensitive internal services. An unauthenticated attacker on an adjacent network could use this path to reach internal services and make configuration changes, creating meaningful integrity and availability risk.
Executive priority
Treat this as high priority for environments using Cisco Intersight Virtual Appliance, especially where management networks are not tightly isolated. The main business risk is unauthorized configuration change or service disruption from a nearby network position.
Technical view
The issue is an access-control weakness, CWE-284, caused by insufficient restrictions on packets received by the external management interface. CVSS 3.1 is 8.3 with adjacent-network attack vector, low complexity, no privileges, no user interaction, and high integrity and availability impact.
Likely exposure
Exposure is most likely where Cisco Intersight Virtual Appliance is deployed and its external management interface is reachable from adjacent or insufficiently trusted network segments. The provided bundle does not enumerate exact affected versions, so asset and version validation must use Cisco guidance.
Exploitation context
The provided sources do not show CISA KEV listing or confirmed active exploitation. The attack is described as unauthenticated but adjacent, meaning an attacker needs network proximity to the management interface rather than arbitrary internet reachability.
Researcher notes
The bundle supports Cisco Intersight Virtual Appliance as the affected product, but not specific version ranges or patch names. Do not assume internet-routable exploitation. Focus validation on management-interface exposure, IPv4 and IPv6 forwarding controls, and Cisco’s advisory details.
Mitigation direction
- Review Cisco’s advisory for affected releases, fixed software, and any official workarounds.
- Restrict management-interface reachability to trusted administrative networks only.
- Validate network segmentation between external management interfaces and internal services.
- Prioritize remediation for appliances in shared, campus, or exposed management networks.
Validation and detection
- Inventory Cisco Intersight Virtual Appliance deployments and record appliance versions.
- Confirm whether external management interfaces are reachable from adjacent untrusted networks.
- Check firewall and routing policy for paths from management interfaces to internal services.
- Review Cisco advisory applicability against each deployed appliance 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
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-284: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-1600 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
- 8.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:H/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:L/I:H/A:H2.85.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.3HighVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210721 Cisco Intersight Virtual Appliance IPv4 and IPv6 Forwarding VulnerabilitiesCVE reference · vendor-advisory, x_refsource_CISCO
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 Access Control
Improper Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.