CVE-2021-1366

SYSTEM code execution via crafted IPC message

Published Feb 17, 2021 · Updated Nov 8, 2024

DLL hijacking in Cisco Secure Client (AnyConnect) for Windows before 4.9.05042 allows local users to execute arbitrary code as SYSTEM. The AnyConnect IPC channel accepts a crafted local message that causes the process to load an insufficiently validated runtime resource. Exploitation requires valid Windows credentials and the VPN Posture (HostScan) Module; Linux, macOS, mobile clients, and ISE Posture-only installations are unaffected.

CVSS severity7.8
High
EPSS probability1.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DLL hijacking in Cisco Secure Client (AnyConnect) for Windows before 4.9.05042 allows local users to execute arbitrary code as SYSTEM. The AnyConnect IPC channel accepts a crafted local message that causes the process to load an insufficiently validated runtime resource. Exploitation requires valid Windows credentials and the VPN Posture (HostScan) Module; Linux, macOS, mobile clients, and ISE Posture-only installations are unaffected.

The record

CVE
CVE-2021-1366
Published
Feb 17, 2021
Updated
Nov 8, 2024
Vendor
ClamAV
Product
Cisco Secure Client
Classifications
CWE-427, CWE-347, T1574.001, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 17, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

ClamAV · Cisco Secure Clientversion=n/a

Published CVSS scores

7.8Cisco Systems, Inc.CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.9NIST National Vulnerability DatabaseAV:L/AC:M/Au:N/C:C/I:C/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-427Uncontrolled Search Path Element
CWE-347Improper Verification of Cryptographic Signature
T1574.001Hijack Execution Flow: DLL Search Order Hijacking
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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