What’s Vulnerable › Vulnerabilities

CVE-2020-3134: Cisco Email Security Appliance Zip Decompression Engine Denial of Service Vulnerability

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-01-26 · updated 2026-06-17
• Weakness: CWE-20

Description

A vulnerability in the zip decompression engine 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. The vulnerability is due to improper validation of zip files. An attacker could exploit this vulnerability by sending an email message with a crafted zip-compressed attachment. A successful exploit could trigger a restart of the content-scanning process, causing a temporary DoS condition. This vulnerability affects Cisco AsyncOS Software for Cisco ESA releases earlier than 13.0.

Affected products

• Cisco Email Security Appliance (ESA): before 13.0 — fixed in 13.0

How to fix

Upgrade to a fixed version: Cisco Email Security Appliance (ESA) 13.0. Check the vendor advisory for mitigations.

References

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-dos-87mBkc8n
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-dos-87mBkc8n

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