CVE-2022-20653Network attack vector

Denial of service via DNS error mishandling

Published Feb 17, 2022 · Updated Nov 6, 2024

Denial of service in Cisco Secure Email Gateway AsyncOS allows remote attackers to interrupt mail processing with crafted email. The DANE email verification component insufficiently handles DNS name-resolution errors while processing specially formatted messages. No authentication is required; a successful message can block management access and further mail processing until recovery, while repeated messages can keep the appliance unavailable.

CVSS severity7.5
High
EPSS probability1.83%
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 Gateway AsyncOS allows remote attackers to interrupt mail processing with crafted email. The DANE email verification component insufficiently handles DNS name-resolution errors while processing specially formatted messages. No authentication is required; a successful message can block management access and further mail processing until recovery, while repeated messages can keep the appliance unavailable.

The record

CVE
CVE-2022-20653
Published
Feb 17, 2022
Updated
Nov 6, 2024
Vendor
ClamAV
Product
Cisco Secure Email Gateway
Classifications
CWE-399, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 17, 2022CVE publishedPublication date reported by the CVE source.
  2. Nov 6, 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=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Secure Email Gatewayversion=n/a

Published CVSS scores

7.5CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-399Resource Management Errors
T1499.004Application or System Exploitation

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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