CVE-2023-20241VulnerabilityPublished 22 Nov 2023Updated 5 Jun 2025

CVE-2023-20241: Cisco Secure Client · Out-of-bounds Read

Affects Cisco Secure ClientSource CVE Database V5

Not known to be exploited · CVSS 5.5 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

5.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Nov 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Cisco Cisco Secure Client	Affected =4.9.00086 =4.9.01095 =4.9.02028 =4.9.03047 =4.9.03049 =4.9.04043 =4.9.04053 =4.9.05042 =4.9.06037 =4.10.00093 =4.10.01075 =4.10.02086 =4.10.03104 =4.10.04065 =4.10.04071 =4.10.05085 =4.10.05095 =4.10.05111 =4.10.06079 =4.10.06090 =4.10.07061 =4.10.07062 =4.10.07073 =5.0.00238 =5.0.00529 =5.0.00556 =5.0.01242 =5.0.02075 =5.0.03072 =5.0.03076 =5.0.04032	Fixed in–

AI-suggested

To mitigate this vulnerability effectively, European organizations should: 1) Identify and inventory all systems running affected versions of Cisco Secure Client, focusing on multi-user environments. 3) Restrict local user access on multi-user systems to trusted personnel only, minimizing the risk of malicious or accidental exploitation. 4) Implement strict user account management and monitoring to detect unauthorized or suspicious logins, especially concurrent sessions on the same host. 5) Consider isolating VPN client usage to single-user systems or virtualized environments to reduce multi-user attack surface. 6) Employ endpoint detection and response (EDR) tools to monitor for abnormal process crashes or network activity related to the VPN Agent service. 7) Educate users about the importance of credential security to prevent unauthorized local access. These targeted steps go beyond generic advice by focusing on the unique multi-user aspect and local authentication requirement of this vulnerability.

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.

Impact

For European organizations, this vulnerability poses a risk primarily to environments where Cisco Secure Client is deployed on multi-user systems, such as shared workstations or terminal servers. The denial of service caused by crashing the VPN Agent service can interrupt secure remote access, potentially halting critical business operations, especially for organizations relying heavily on VPNs for remote workforce connectivity. While the vulnerability does not expose sensitive data or allow privilege escalation, the loss of VPN service availability can degrade productivity and delay incident response activities. Organizations in sectors with high dependency on secure remote access, such as finance, healthcare, government, and critical infrastructure, could experience operational disruptions. Additionally, the requirement for local authenticated access limits the threat to insider attackers or compromised user accounts, which remains a relevant concern for insider threat mitigation in European enterprises.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-accsc-dos-9SLzkZ8 (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 7 Jul 2025, 12:55 UTC

Technical details

References

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