CVE-2020-3529
Published: April 11, 2026
Official Description
A vulnerability in the SSL VPN negotiation process for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to inefficient direct memory access (DMA) memory management during the negotiation phase of an SSL VPN connection. An attacker could exploit this vulnerability by sending a steady stream of crafted Datagram TLS (DTLS) traffic to an affected device. A successful exploit could allow the attacker to exhaust DMA memory on the device and cause a DoS condition.
Risk Analysis
A vulnerability in the SSL VPN negotiation process of Cisco ASA and FTD Software can lead to a denial of service (DoS) condition. An unauthenticated, remote attacker can cause a device reload by sending a steady stream of crafted Datagram TLS (DTLS) traffic, exhausting DMA memory. The flaw is urgent because it has been confirmed as exploited in the wild by CISA.
Active exploitation of this vulnerability has been observed in the wild, and it is listed in CISA's KEV catalog. The flaw is remotely exploitable without authentication.
Apply the latest security updates and patches for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software. Monitor DTLS traffic for anomalies that might indicate a DoS attack.
Technical Analysis
CVE-2020-3529 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2020-3529 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Affected Vendors & Products
Exploit & PoC Resources
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2020-3529 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1