Anyconnect Secure Mobility ClientApplication · Cisco
CVE-2021-1567
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA vulnerability in the DLL loading mechanism of Cisco AnyConnect Secure Mobility Client for Windows could allow an authenticated, local attacker to perform a DLL hijacking attack on an affected device if the VPN Posture (HostScan) Module is installed on the AnyConnect client. This vulnerability is due to a race condition in the signature verification process for DLL files that are loaded on an affected device. An attacker could exploit this vulnerability by sending a series of crafted interprocess communication (IPC) messages to the AnyConnect process. A successful exploit could allow the attacker to execute arbitrary code on the affected device with SYSTEM privileges. To exploit this vulnerability, the attacker must have valid credentials on the Windows system.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceThis is a DLL hijacking vulnerability in Cisco AnyConnect Secure Mobility Client for Windows caused by a race condition in the DLL signature verification process. An authenticated local attacker with valid Windows credentials can send crafted IPC messages to the AnyConnect process when the VPN Posture (HostScan) Module is installed, allowing arbitrary code execution with SYSTEM privileges.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Anyconnect Secure Mobility ClientApplication
< 4.10.01075CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- High
- Privileges
- Low
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify Cisco AnyConnect is installedCheck for the presence of Cisco AnyConnect Secure Mobility Client on the Windows system. Look for the installation in Program Files or check Windows registry under HKLM\SOFTWARE\Cisco SystemsAffected if AnyConnect is not installed on the system
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Determine installed AnyConnect versionOpen Add or Remove Programs (appwiz.cpl) and find 'Cisco AnyConnect Secure Mobility Client' to view the installed version, or query the Windows Installer database for the version informationAffected if The displayed version number is lower than 4.10.01075
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Check if HostScan module is presentInspect the AnyConnect installation directory for the HostScan module components. The HostScan module is typically found under the VPN Posture or hostscan subdirectory within the AnyConnect installation folderAffected if The HostScan (VPN Posture) module is installed alongside AnyConnect
The system is affected if AnyConnect Secure Mobility Client is installed with a version lower than 4.10.01075 AND the HostScan (VPN Posture) module is present on the system.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data4.10.01075
Apply the Cisco security patch for this vulnerability. If the HostScan module is not required, consider removing it to reduce the attack surface.
Fix this in Anyconnect Secure Mobility Client
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 h
- Testing1.0 h
- Review / QA0.5 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1567 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-1567 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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