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CVE-2019-1905: Cisco Email Security Appliance GZIP Content Filter Bypass Vulnerability

• Severity: medium (CVSS 5.8 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-06-20 · updated 2026-06-17
• Weakness: CWE-20

Description

A vulnerability in the GZIP decompression engine of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass configured content filters on the device. The vulnerability is due to improper validation of GZIP-formatted files. An attacker could exploit this vulnerability by sending a malicious file inside a crafted GZIP-compressed file. A successful exploit could allow the attacker to bypass configured content filters that would normally drop the email.

Affected products

• Cisco Email Security Appliance (ESA): 11.1.2, 12.0.0

References

• http://www.securityfocus.com/bid/108856
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190619-esa-bypass
• http://www.securityfocus.com/bid/108856
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190619-esa-bypass

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