Security readout for executives and security teams
Plain-English summary
This flaw lets a logged-in Windows user potentially turn Cisco AnyConnect with the VPN Posture (HostScan) module into SYSTEM-level code execution. It is not a remote internet worm scenario, but it can turn a compromised low-privilege account on a VPN endpoint into full machine control.
Executive priority
Treat this as high priority for VPN endpoint fleets, especially where users have local access or endpoints are shared. It supports privilege escalation after initial access, so it can materially worsen workstation compromise even without remote unauthenticated exploitation.
Technical view
CVE-2021-1366 is an IPC validation weakness in Cisco AnyConnect Secure Mobility Client for Windows when VPN Posture (HostScan) is installed. A local authenticated attacker can send a crafted IPC message that triggers unsafe runtime resource loading, enabling DLL hijacking and arbitrary code execution as SYSTEM.
Likely exposure
Exposure is limited to Windows endpoints running Cisco AnyConnect Secure Mobility Client with the VPN Posture (HostScan) module installed. The source bundle does not identify exact affected versions, so asset inventory must be matched against Cisco's advisory.
Exploitation context
The attacker needs valid Windows credentials and local access. Successful exploitation provides SYSTEM privileges. The CVE is not marked KEV in the bundle, and no cited source here confirms active exploitation.
Researcher notes
Key constraints are local attack vector, low privileges required, no user interaction, and SYSTEM impact. The vulnerable condition depends on HostScan presence. The provided sources do not include affected version ranges, confirmed exploitation, or specific fixed builds.
Mitigation direction
- Review Cisco's advisory for fixed releases or official workarounds.
- Inventory AnyConnect Windows clients with VPN Posture (HostScan) installed.
- Prioritize remediation on shared, high-risk, or frequently targeted endpoints.
- Remove unused HostScan deployments where business requirements allow.
- Restrict local account access on systems awaiting vendor-directed remediation.
Validation and detection
- Confirm AnyConnect Secure Mobility Client is installed on Windows endpoints.
- Verify whether VPN Posture (HostScan) is installed on each client.
- Compare deployed versions against Cisco's advisory guidance.
- Review endpoint alerts for unexpected SYSTEM-level process activity near AnyConnect.
- Document systems where version data or HostScan status is unavailable.
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-347: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-1366 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210217 Cisco AnyConnect Secure Mobility Client for Windows with VPN Posture (HostScan) Module DLL Hijacking VulnerabilityCVE 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 Verification of Cryptographic Signature
Improper Verification of Cryptographic Signature represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.