CVE-2023-20042
MediumCVSS 6.8Exploitation Probability (EPSS)
Low risk49th percentile - higher than 49% of all known CVEs
Summary
A vulnerability in the AnyConnect SSL VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This is due to an implementation error in SSL/TLS session handling that can prevent the release of a session handler under specific conditions. An attacker could exploit this by sending crafted SSL/TLS traffic, increasing the probability of session handler leaks and eventually depleting the available pool.
Risk Assessment
The risk is that an attacker can deplete the session handler pool, preventing new VPN sessions and causing a DoS.
Recommendation
Apply Cisco updates for ASA and FTD. Monitor SSL/TLS traffic and consider limiting concurrent VPN sessions.
Other vulnerabilities in Cisco Adaptive Security Appliance (ASA) Software
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The DHCPv6 relay implementation in Cisco Adaptive Security Appliance (ASA) Software 9.4.1 allows remote attackers to cause a denial of service (device reload) via crafted DHCPv6 packets.
- CVE-2015-0677High
The XML parser in Cisco Adaptive Security Appliance (ASA) Software before version 8.4(7.28), 8.6(1.17), 9.0(4.33), 9.1(6), 9.2(3.4), and 9.3(3) is vulnerable to an attack that can lead to denial of service via a crafted XML document. This attack can result in VPN outages or device reloads.
- CVE-2015-0676High
The DNS implementation in Cisco Adaptive Security Appliance (ASA) Software before versions 7.2(5.16), 8.2(5.57), 8.3(2.44), 8.4(7.28), 8.5(1.24), 8.6(1.17), 8.7(1.16), 9.0(4.33), 9.1(6.1), 9.2(3.4), and 9.3(3) is vulnerable to man-in-the-middle attacks that can lead to denial of service by triggering DNS queries and sending crafted responses.
- CVE-2015-0675High
The failover IPsec implementation in Cisco Adaptive Security Appliance (ASA) Software before version 9.1(6), 9.2(3.3), and 9.3(3) does not properly validate failover communication messages, allowing remote attackers to reconfigure an ASA device.
- CVE-2014-2129High
The SIP inspection engine in Cisco Adaptive Security Appliance (ASA) Software before versions 8.2(5.48), 8.4(6.5), 9.0(3.1), and 9.1(2.5) allows remote attackers to cause a denial of service via crafted SIP packets.
- CVE-2014-2127High
Cisco Adaptive Security Appliance (ASA) Software versions before 8.2(5.48), 8.3 before 8.3(2.40), 8.4 before 8.4(7.9), 8.6 before 8.6(1.13), 9.0 before 9.0(4.1), and 9.1 before 9.1(4.3) does not properly process management-session information during privilege validation for SSL VPN portal connections. This allows remote authenticated users to gain privileges by establishing a Clientless SSL VPN session and entering crafted URLs.
- CVE-2014-2126High
Cisco Adaptive Security Appliance (ASA) Software versions before 8.2(5.47), 8.4(7.5), 8.7(1.11), 9.0(3.10), and 9.1(3.4) allows remote authenticated users to gain privileges by leveraging level-0 ASDM access.
- CVE-2025-20182High
A vulnerability in the Internet Key Exchange version 2 (IKEv2) protocol processing of Cisco Adaptive Security Appliance (ASA) Software, Cisco Firepower Threat Defense (FTD) Software, Cisco IOS Software, and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The issue is due to insufficient input validation when processing IKEv2 messages. Sending crafted IKEv2 traffic can cause the device to reload, resulting in a DoS condition.
- CVE-2024-20426High
A vulnerability in the Internet Key Exchange version 2 (IKEv2) protocol for VPN termination of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The issue is due to insufficient input validation. Sending crafted IKEv2 traffic can cause the device to reload, resulting in a DoS condition.
- CVE-2024-20382Medium
A vulnerability in the VPN web client services feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct a cross-site scripting (XSS) attack against a browser accessing an affected device. The issue is due to improper validation of user-supplied input to application endpoints.
Original NVD description (English source)
A vulnerability in the AnyConnect SSL VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to an implementation error within the SSL/TLS session handling process that can prevent the release of a session handler under specific conditions. An attacker could exploit this vulnerability by sending crafted SSL/TLS traffic to an affected device, increasing the probability of session handler leaks. A successful exploit could allow the attacker to eventually deplete the available session handler pool, preventing new sessions from being established and causing a DoS condition.