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Vulnerability record · CVE-2020-3548 · published 18 November 2024

CVE-2020-3548: Cisco email security appliance vulnerability

Cisco · Email Security Appliance

A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco AsyncOS software for Cisco 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. The 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.

7.5 CVSS 3.1 High EPSS 0.84% · top 43.7% CWE-407 · CWE-407
7.5CVSS 3.1 base score
0.84%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
1References
17 Jun 2026Last modified by NVD

Description

A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco AsyncOS software for Cisco 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. The 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.

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

Affected products

1 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-esa-tls-dos-xW53TBhb Vendor Advisory

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Related vulnerabilities

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

9.8CVE-2022-20798Cisco email security appliance improper authentication vulnerabilityA vulnerability in the external authentication functionality of Cisco Secure Email and Web Manager, formerly known as Cisco Security Management Appli…EPSS 1.5%8.6CVE-2019-1947Cisco email security appliance improper input validation vulnerabilityA vulnerability in the email message filtering feature of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthentica…EPSS 1.9%7.8CVE-2015-6321Cisco web security appliance vulnerabilityCisco AsyncOS before 8.5.7-042, 9.x before 9.1.0-032, 9.1.x before 9.1.1-023, and 9.5.x and 9.6.x before 9.6.0-042 on Email Security Appliance (ESA) …EPSS 2.8%7.8CVE-2015-6291Cisco email security appliance improper input validation vulnerabilityCisco AsyncOS before 8.5.7-043, 9.x before 9.1.1-023, and 9.5.x and 9.6.x before 9.6.0-046 on Email Security Appliance (ESA) devices mishandles malfo…EPSS 1.9%7.7CVE-2022-20664Cisco email security appliance information exposure vulnerabilityA vulnerability in the web management interface of Cisco Secure Email and Web Manager, formerly Cisco Security Management Appliance (SMA), and Cisco …EPSS 1.0%7.5CVE-2022-20960Cisco email security appliance uncontrolled resource consumption vulnerabilityA vulnerability in Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated remote attacker to cause a denial o…EPSS 0.83%7.5CVE-2020-3133Cisco email security appliance improper input validation vulnerabilityA vulnerability in the email message scanning of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remo…EPSS 1.4%7.5CVE-2019-1921Cisco email security appliance improper input validation vulnerabilityA vulnerability in the attachment scanning of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote …EPSS 1.4%

Source: NIST National Vulnerability Database (record CVE-2020-3548), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.