CVE-2020-3548Network attack vector

Service degradation via crafted TLS packet processing

Published Nov 18, 2024 · Updated Nov 18, 2024

Denial of service in Cisco Secure Email 13.5.1-277 and earlier allows remote attackers to degrade performance via crafted TLS packets. The AsyncOS TLS implementation processes a series of crafted packets inefficiently, sustaining high CPU utilization. No authentication is required; the appliance remains operative, but email-security response time and overall performance degrade.

CVSS severity5.3
Medium
EPSS probability0.84%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco Secure Email 13.5.1-277 and earlier allows remote attackers to degrade performance via crafted TLS packets. The AsyncOS TLS implementation processes a series of crafted packets inefficiently, sustaining high CPU utilization. No authentication is required; the appliance remains operative, but email-security response time and overall performance degrade.

The record

CVE
CVE-2020-3548
Published
Nov 18, 2024
Updated
Nov 18, 2024
Vendor
ClamAV
Product
Cisco Secure Email
Classifications
CWE-407, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 18, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 18, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=13.5.1-277
  2. Affected versionversion=N/A

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Secure Emailversion=0 <=13.5.1-277; version=N/A

Published CVSS scores

5.3CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:X/RL:X/RC:X

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-407Inefficient Algorithmic Complexity
T1499.002Service Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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