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Fencer Vulns
high 7.5

CVE-2022-20653 json

Cisco Email Security Appliance DNS Verification Denial of Service Vulnerability

published 2022-02-17 4 y ago modified 2026-06-17 4 mo ago also EUVD-2022-25903

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.8%
EPSS 1.8% chance of exploitation in 30 days, percentile 78%
public exploits
0
none known

Summary

A vulnerability in the DNS-based Authentication of Named Entities (DANE) email verification component of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient error handling in DNS name resolution by the affected software. An attacker could exploit this vulnerability by sending specially formatted email messages that are processed by an affected device. A successful exploit could allow the attacker to cause the device to become unreachable from management interfaces or to process additional email messages for a period of time until the device recovers, resulting in a DoS condition. Continued attacks could cause the device to become completely unavailable, resulting in a persistent DoS condition.

Patch / fix

  • cisco asyncos 13.0.3, 13.5.4.102, 14.0.2.020

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
2 y ago

Exploit prediction

1.83% chance of exploitation in the next 30 days, higher than 78% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 7.1 AV:N/AC:M/Au:N/C:N/I:N/A:C

Affected products

  • Cisco Cisco Email Security Appliance (ESA)

Classification

Weakness
  • CWE-399 Resource Management Errors

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.