What’s Vulnerable › Vulnerabilities

CVE-2019-12706: Cisco Email Security Appliance Filter Bypass Vulnerability

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-10-02 · updated 2026-06-17
• Weakness: CWE-20

Description

A vulnerability in the Sender Policy Framework (SPF) functionality of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the configured user filters on an affected device. The vulnerability exists because the affected software insufficiently validates certain incoming SPF messages. An attacker could exploit this vulnerability by sending a custom SPF packet to an affected device. A successful exploit could allow the attacker to bypass the configured header filters, which could allow malicious content to pass through the device.

Affected products

• Cisco Email Security Appliance: before 13.5.0 — fixed in 13.5.0

How to fix

Upgrade to a fixed version: Cisco Email Security Appliance 13.5.0. Check the vendor advisory for mitigations.

References

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20191002-esa-bypass
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20191002-esa-bypass

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