PatchTheCVECVE-2020-3548: A vulnerability in the Transport Layer Security (TLS) protocol implementation of Cisco AsyncOS software f
CVE-2020-3548 is a medium-severity flaw (CVSS 5.3) affecting email security appliance. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 craft
Why this priority
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.8% (top 42%) |
| CISA exploited list | No |
| Weakness | CWE-407 |
| Published | 2024-11-18 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2020-3548?
email security appliance: upgrade to newer than 13.5.1-277. Exact commands for each OS are on this page.
Is CVE-2020-3548 being exploited?
CVE-2020-3548 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2020-3548 affect?
CVE-2020-3548 affects email security appliance. Severity is medium (CVSS 5.3). 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 affecte
How urgent is CVE-2020-3548?
Priority 38/100. Remotely exploitable, no login, no user action