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

> Unauthenticated remote attackers can bypass filtering protections by sending obfuscated payloads, delivering malicious content to protected systems.

- **Severity:** Medium 5.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Nov 2019
- **Updated:** 19 Nov 2024
- **Also known as:** GHSA-55w6-hghf-mfpw

## What is CVE-2019-1981?

CVE-2019-1981 is a medium-severity vulnerability in Cisco Secure Firewall Management Center, published on 5 Nov 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-20 (Improper Input Validation), CWE-264

## Which versions are affected by CVE-2019-1981?

It affects 3 products.


Products: Cisco Firepower Services Software for Asa, Cisco Secure Firewall Management Center, Cisco Secure Firewall Threat Defense.

## How do I fix CVE-2019-1981?

No fix has been published for CVE-2019-1981 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-1981 being exploited?

There is no known exploitation of CVE-2019-1981 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Secure Firewall Management Center

- [CVE-2022-20918](https://insights.sbomify.com/CVE-2022-20918/): Hardcoded credentials in Cisco FirePOWER Services Software for ASA (high 7.5)
- [CVE-2019-1978](https://insights.sbomify.com/CVE-2019-1978/): Cisco Firepower Threat Defense Software Stream Reassembly Bypass Vulnerability (medium 5.8)
- [CVE-2019-1980](https://insights.sbomify.com/CVE-2019-1980/): Cisco Firepower Threat Defense Software Nonstandard Protocol Detection Bypass Vulnerability (medium 5.8)
- [CVE-2019-1982](https://insights.sbomify.com/CVE-2019-1982/): Cisco Firepower Threat Defense Software HTTP Filtering Bypass Vulnerability (medium 5.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-1981 and fix it if it is affected.

What it is: CVE-2019-1981 is a medium-severity vulnerability in Cisco Secure Firewall Management Center, published on 5 Nov 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2019-1981 in the wild and no public exploit code.

Affected product: Cisco Secure Firewall Management Center. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2019-1981/ (Markdown: https://insights.sbomify.com/CVE-2019-1981/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-1981
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-1981
- OSV: https://osv.dev/vulnerability/CVE-2019-1981

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-1981/
Summaries are generated and may contain mistakes; the official description above is the record.