Cisco Firepower Threat Defense Software NULL Character Obfuscation Detection Bypass Vulnerability

published 2019-11-05 7 y ago modified 2026-08-11 2 mo ago also EUVD-2019-10538

cvss: 5.8; version 3.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.0%; EPSS 1.0% chance of exploitation in 30 days, percentile 64%
public exploits: 0; none known

A vulnerability in the normalization functionality of Cisco Firepower Threat Defense Software, Cisco FirePOWER Services Software for ASA, and Cisco Firepower Management Center Software could allow an unauthenticated, remote attacker to bypass filtering protections. The vulnerability is due to insufficient normalization of a text-based payload. An attacker could exploit this vulnerability by sending traffic that contains specifically obfuscated payloads through an affected device. An exploit could allow the attacker to bypass filtering and deliver malicious payloads to protected systems that would otherwise be blocked.

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 23 mo ago (2024-11-19)

Exploit prediction

1.04% chance of exploitation in the next 30 days, higher than 64% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.0	5.8	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
NVD	3.1	5.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N

Affected products

Cisco Cisco Firepower Threat Defense Software

Classification

Weakness

CWE-264 Permissions, Privileges, and Access Controls
CWE-20 Improper Input Validation

References

tools.cisco.com /security/center/content/CiscoSecurityAdvisory/cisco-sa-20190816-ftd-null
vendor-advisory

Sources

CVE List CVE-2019-1981
NVD CVE-2019-1981

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Summary