CVE-2019-1955: Cisco Email Security Appliance Header Injection Vulnerability

Severity: high (CVSS 7.5 v3.1)
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: 2019-08-08 · 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 Appliances (ESA) could allow an unauthenticated, remote attacker to bypass configured user filters on the device. The vulnerability is due to incomplete input and validation checking mechanisms for certain SPF messages that are sent to an affected device. An attacker could exploit this vulnerability by sending a customized SPF packet to an affected device. A successful exploit could allow the attacker to bypass the header filters that are configured for the affected device, which could allow malicious content to pass through the device.

Affected products

Cisco Email Security Appliance: before 4.0mr1; 12.0 — fixed in 4.0mr1

How to fix

Upgrade to a fixed version: Cisco Email Security Appliance 4.0mr1. Check the vendor advisory for mitigations.

References

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