Security readout for executives and security teams
Plain-English summary
Cisco AnyConnect on Windows can be abused by a local signed-in user when the VPN Posture (HostScan) module is installed. The issue can let that user run code as SYSTEM, turning a normal endpoint account into full device control. It is high risk but requires local access and a higher-complexity race condition.
Executive priority
Treat this as a high-priority endpoint privilege escalation issue for environments using AnyConnect posture checks. It is not a remote internet-facing compromise by itself, but it can turn an already-compromised or malicious local account into full device control.
Technical view
The vulnerability is a DLL hijacking issue caused by a race condition in DLL signature verification. An authenticated local attacker can send crafted IPC messages to the AnyConnect process. Successful exploitation may execute arbitrary code with SYSTEM privileges. The CVSS 3.1 score is 7.0 with local attack vector, low privileges required, and high complexity.
Likely exposure
Exposure is limited to Windows systems running Cisco AnyConnect Secure Mobility Client where the VPN Posture, also called HostScan, module is installed. The source bundle does not provide exact affected version ranges.
Exploitation context
The CVE is not listed as CISA KEV in the provided data, and the bundle contains no evidence of active exploitation. Exploitation requires valid Windows credentials on the target and local access, but successful exploitation provides SYSTEM-level impact.
Researcher notes
Key constraints are local authenticated access, high attack complexity, and HostScan module presence. The source data identifies CWE-367 and a DLL signature verification race. Exact version ranges, fixed builds, and Cisco workaround details are not included in the bundle.
Mitigation direction
- Check Cisco’s advisory for affected and fixed AnyConnect releases.
- Upgrade affected clients and HostScan components using Cisco-supported guidance.
- Inventory Windows endpoints for AnyConnect with the VPN Posture module installed.
- Prioritize systems where standard users can sign in locally.
- Limit unnecessary local user access on affected Windows endpoints.
Validation and detection
- Confirm AnyConnect is installed on Windows endpoints.
- Confirm whether the VPN Posture or HostScan module is installed.
- Compare installed versions against Cisco’s advisory.
- Verify remediation status through endpoint management or vulnerability scanning.
- Review endpoint logs for unusual AnyConnect process activity.
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-367: 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-2021-1567 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 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:H/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:H/PR:L/UI:N/S:U/C:H/I:H/A:H15.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7HighVector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210616 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.
Time-of-check Time-of-use (TOCTOU) Race Condition
Time-of-check Time-of-use (TOCTOU) Race Condition represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.