Cisco Email Security Appliance Content Filter Bypass Vulnerability

published 2020-09-23 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-24404

cvss: 5.8; version 3.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.4%; EPSS 1.4% chance of exploitation in 30 days, percentile 72%
public exploits: 0; none known

A vulnerability in the email message scanning of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass configured filters on the device. The vulnerability is due to improper validation of incoming emails. An attacker could exploit this vulnerability by sending a crafted email message to a recipient protected by the ESA. A successful exploit could allow the attacker to bypass the configured content filters, which could allow malicious content to pass through the device.

Patch / fix

fixed in 1

cisco email_security_appliance 13.0

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 23 mo ago (2024-11-13)

Exploit prediction

1.38% chance of exploitation in the next 30 days, higher than 72% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.0	5.8	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N

Affected products

Cisco Cisco Email Security Appliance (ESA)

Classification

Weakness

CWE-20 Improper Input Validation

References

tools.cisco.com /security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-bypass-5Cdv2HMA
vendor-advisory

Sources

CVE List CVE-2020-3133
NVD CVE-2020-3133

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Summary