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Vulnerability record · CVE-2023-20240 · published 22 November 2023

CVE-2023-20240: Cisco anyconnect secure mobility client out-of-bounds read vulnerability

Cisco · Anyconnect Secure Mobility Client

Multiple vulnerabilities in Cisco Secure Client Software, formerly AnyConnect Secure Mobility Client, could allow an authenticated, local attacker to cause a denial of service (DoS) condition on an affected system. These vulnerabilities are due to an out-of-bounds memory read from Cisco Secure Client Software. An attacker could exploit these vulnerabilities by logging in to an affected device at the same time that another user is accessing Cisco Secure Client on the same system, and then sending crafted packets to a port on that local host. A successful exploit could allow the attacker to crash the VPN Agent service, causing it to be unavailable to all users of the system. To exploit these vulnerabilities, the attacker must have valid credentials on a multi-user system.

5.5 CVSS 3.1 Medium EPSS 0.20% · top 91.5% CWE-125 · Out-of-bounds read
5.5CVSS 3.1 base score
0.20%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

Multiple vulnerabilities in Cisco Secure Client Software, formerly AnyConnect Secure Mobility Client, could allow an authenticated, local attacker to cause a denial of service (DoS) condition on an affected system. These vulnerabilities are due to an out-of-bounds memory read from Cisco Secure Client Software. An attacker could exploit these vulnerabilities by logging in to an affected device at the same time that another user is accessing Cisco Secure Client on the same system, and then sending crafted packets to a port on that local host. A successful exploit could allow the attacker to crash the VPN Agent service, causing it to be unavailable to all users of the system. To exploit these vulnerabilities, the attacker must have valid credentials on a multi-user system.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-accsc-dos-9SLzkZ8 Issue TrackingVendor Advisory
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-accsc-dos-9SLzkZ8 Issue TrackingVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.8CVE-2020-3433Cisco AnyConnect Windows client DLL hijacking via IPC channelCisco AnyConnect Secure Mobility Client for Windows fails to properly validate resources loaded at run time, allowing a DLL hijacking attack through …KEVEPSS 10%analysed6.5CVE-2020-3153Cisco AnyConnect Windows Installer Path Handling Privilege EscalationThe Cisco AnyConnect Secure Mobility Client for Windows installer mishandles directory paths, letting an authenticated local user copy attacker-suppl…KEVEPSS 28%analysed9.3CVE-2012-3088Cisco anyconnect secure mobility client vulnerabilityCisco AnyConnect Secure Mobility Client 3.1.x before 3.1.00495, and 3.2.x, does not check whether an HTTP request originally contains ScanSafe header…EPSS 1.8%9.3CVE-2012-2493Cisco anyconnect secure mobility client improper input validation vulnerabilityThe VPN downloader implementation in the WebLaunch feature in Cisco AnyConnect Secure Mobility Client 2.x before 2.5 MR6 on Windows, and 2.x before 2…EPSS 3.9%9.3CVE-2011-2040Cisco anyconnect secure mobility client improper input validation vulnerabilityThe helper application in Cisco AnyConnect Secure Mobility Client (formerly AnyConnect VPN Client) before 2.5.3041, and 3.0.x before 3.0.629, on Linu…EPSS 11%8.2CVE-2024-20337Cisco secure client vulnerabilityA vulnerability in the SAML authentication process of Cisco Secure Client could allow an unauthenticated, remote attacker to conduct a carriage retur…EPSS 30%7.8CVE-2025-20206Cisco secure client improper verification of cryptographic signature vulnerabilityA vulnerability in the interprocess communication (IPC) channel of Cisco Secure Client for Windows could allow an authenticated, local attacker to pe…EPSS 0.18%7.8CVE-2023-20178Cisco anyconnect secure mobility client incorrect default permissions vulnerabilityA vulnerability in the client update process of Cisco AnyConnect Secure Mobility Client Software for Windows and Cisco Secure Client Software for Win…EPSS 5.4%

Source: NIST National Vulnerability Database (record CVE-2023-20240), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.