# CVE-2020-1999: PAN-OS: Threat signatures are evaded by specifically crafted packets

> Attackers can evade threat detection by sending crafted TCP packets, allowing malicious traffic to bypass security controls on PAN-OS firewalls.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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:** 12 Nov 2020
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-6p97-xh7r-7cmv

## What is CVE-2020-1999?

CVE-2020-1999 is a medium-severity vulnerability in Paloaltonetworks Pan-Os, published on 12 Nov 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability exists in the Palo Alto Network PAN-OS signature-based threat detection engine that allows an attacker to communicate with devices in the network in a way that is not analyzed for threats by sending data through specifically crafted TCP packets. This technique evades signature-based threat detection. This issue impacts: PAN-OS 8.1 versions earlier than 8.1.17; PAN-OS 9.0 versions earlier than 9.0.11; PAN-OS 9.1 versions earlier than 9.1.5; All versions of PAN-OS 7.1 and PAN-OS 8.0.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions)

## Which versions are affected by CVE-2020-1999?

It affects 1 product.


Products: Paloaltonetworks Pan-Os.

## How do I fix CVE-2020-1999?

No fix has been published for CVE-2020-1999 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-1999 being exploited?

There is no known exploitation of CVE-2020-1999 in the wild and no public exploit code.

## Other vulnerabilities in Paloaltonetworks Pan-Os

- [CVE-2024-3400](https://insights.sbomify.com/CVE-2024-3400/): Palo Alto Networks PAN-OS Command Injection (critical 10.0, exploited in the wild)
- [CVE-2020-2021](https://insights.sbomify.com/CVE-2020-2021/): Palo Alto Networks PAN-OS Authentication Bypass (critical 10.0, exploited in the wild)
- [CVE-2017-15944](https://insights.sbomify.com/CVE-2017-15944/): Palo Alto Networks PAN-OS Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2026-0300](https://insights.sbomify.com/CVE-2026-0300/): Palo Alto Networks PAN-OS Out-of-bounds Write (critical 9.3, exploited in the wild)
- [CVE-2024-0012](https://insights.sbomify.com/CVE-2024-0012/): Palo Alto Networks PAN-OS Management Interface Authentication Bypass (critical 9.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-1999 and fix it if it is affected.

What it is: CVE-2020-1999 is a medium-severity vulnerability in Paloaltonetworks Pan-Os, published on 12 Nov 2020. 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-2020-1999 in the wild and no public exploit code.

Affected product: Paloaltonetworks Pan-Os. 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-2020-1999/ (Markdown: https://insights.sbomify.com/CVE-2020-1999/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1999
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1999
- OSV: https://osv.dev/vulnerability/CVE-2020-1999

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-1999/
Summaries are generated and may contain mistakes; the official description above is the record.