{"id":"CVE-2020-3548","aliases":["EUVD-2020-24819","GHSA-r24r-r242-xm9f"],"status":"published","title":"Cisco Email Security Appliance Denial Of Service Vulnerability","description":"A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco\u0026nbsp;AsyncOS software for Cisco\u0026nbsp;Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause high CPU usage on an affected device, resulting in a denial of service (DoS) condition.\r\nThe vulnerability is due to inefficient processing of incoming TLS traffic. An attacker could exploit this vulnerability by sending a series of crafted TLS packets to an affected device. A successful exploit could allow the attacker to trigger a prolonged state of high CPU utilization. The affected device would still be operative, but response time and overall performance may be degraded.There are no workarounds that address this vulnerability.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/RL:X/RC:X/E:X","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00843,"percentile":0.58216,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-407"],"published":"2024-11-18T15:53:40Z","modified":"2026-06-17T03:18:34Z","products":[{"vendor":"cisco","product":"cisco secure email"},{"vendor":"cisco","product":"email_security_appliance"},{"vendor":"cisco","product":"secure_email"}],"references":[{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-tls-dos-xW53TBhb","tags":["Vendor Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-3548"},{"url":"https://github.com/advisories/GHSA-r24r-r242-xm9f"}],"sources":{"cve":[{"id":"CVE-2020-3548","title":"Cisco Email Security Appliance Denial Of Service Vulnerability","description":"A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco\u0026nbsp;AsyncOS software for Cisco\u0026nbsp;Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause high CPU usage on an affected device, resulting in a denial of service (DoS) condition.\r\nThe vulnerability is due to inefficient processing of incoming TLS traffic. An attacker could exploit this vulnerability by sending a series of crafted TLS packets to an affected device. A successful exploit could allow the attacker to trigger a prolonged state of high CPU utilization. The affected device would still be operative, but response time and overall performance may be degraded.There are no workarounds that address this vulnerability.","status":"published","published":"2024-11-18T15:53:40.744Z","modified":"2024-11-18T16:32:04.999Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/RL:X/RC:X/E:X","level":"medium","assessor":"cna"}],"cwes":["CWE-407"],"updated_at":"2026-11-02T14:35:51.923913Z"}],"euvd":[{"id":"EUVD-2020-24819","description":"A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco\u0026nbsp;AsyncOS software for Cisco\u0026nbsp;Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause high CPU usage on an affected device, resulting in a denial of service (DoS) condition.\r\nThe vulnerability is due to inefficient processing of incoming TLS traffic. An attacker could exploit this vulnerability by sending a series of crafted TLS packets to an affected device. A successful exploit could allow the attacker to trigger a prolonged state of high CPU utilization. The affected device would still be operative, but response time and overall performance may be degraded.There are no workarounds that address this vulnerability.","status":"published","published":"2024-11-18T15:53:40Z","modified":"2024-11-18T16:32:04Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/RL:X/RC:X/E:X","level":"medium"}],"updated_at":"2026-11-03T00:04:57.054288Z"}],"ghsa":[{"id":"GHSA-r24r-r242-xm9f","title":"A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco\u0026nbsp...","description":"A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco\u0026nbsp;AsyncOS software for Cisco\u0026nbsp;Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause high CPU usage on an affected device, resulting in a denial of service (DoS) condition.\nThe vulnerability is due to inefficient processing of incoming TLS traffic. An attacker could exploit this vulnerability by sending a series of crafted TLS packets to an affected device. A successful exploit could allow the attacker to trigger a prolonged state of high CPU utilization. The affected device would still be operative, but response time and overall performance may be degraded.There are no workarounds that address this vulnerability.","status":"published","published":"2024-11-18T18:30:56Z","modified":"2024-11-18T18:31:05Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-407"],"updated_at":"2026-11-02T14:58:52.476096Z"}],"nvd":[{"id":"CVE-2020-3548","description":"A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco\u0026nbsp;AsyncOS software for Cisco\u0026nbsp;Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause high CPU usage on an affected device, resulting in a denial of service (DoS) condition.\r\nThe vulnerability is due to inefficient processing of incoming TLS traffic. An attacker could exploit this vulnerability by sending a series of crafted TLS packets to an affected device. A successful exploit could allow the attacker to trigger a prolonged state of high CPU utilization. The affected device would still be operative, but response time and overall performance may be degraded.There are no workarounds that address this vulnerability.","status":"published","published":"2024-11-18T16:15:08.1Z","modified":"2026-06-17T03:18:34.12Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"primary"}],"cwes":["CWE-407"],"updated_at":"2026-11-02T14:06:48.591569Z"}]}}