How severe is CVE-2019-1955?

CVE-2019-1955 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2019-1955 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-1955?

CVE-2019-1955 primarily affects Cisco Email Security Appliance Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-1955?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2019-1955 published?

CVE-2019-1955 was published on 2019-08-08 and last updated on 2026-06-17.

CVE-2019-1955

CVE-2019-1955 is a high-severity vulnerability in Cisco Email Security Appliance Firmware with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (69th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Cisco Email Security Appliance Firmware
Published: 2019-08-08
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2019-1955?: 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.
How severe is CVE-2019-1955?: CVE-2019-1955 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2019-1955 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (69th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-1955?: CVE-2019-1955 primarily affects Cisco Email Security Appliance Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-1955?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2019-1955 published?: CVE-2019-1955 was published on 2019-08-08 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-esm-inject

Affected products (2)

cpe:2.3:o:cisco:email_security_appliance_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:cisco:email_security_appliance_firmware:12.0:*:*:*:*:*:*:*

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