# CVE-2018-20798: Security feature bypass in n/a

> Incompatible block durations between pfSense and sshguard allow attackers to bypass intended access restrictions.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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:** 1 Mar 2019
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-pjhq-f4xq-m288

## What is CVE-2018-20798?

CVE-2018-20798 is a high-severity vulnerability in n/a, published on 1 Mar 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The expiretable configuration in pfSense 2.4.4_1 establishes block durations that are incompatible with the block durations implemented by sshguard, which might make it easier for attackers to bypass intended access restrictions.

Weakness: CWE-732 (Incorrect Permission Assignment for Critical Resource)

## Which versions are affected by CVE-2018-20798?

It affects 1 product.


Products: Netgate Pfsense.

## How do I fix CVE-2018-20798?

No fix has been published for CVE-2018-20798 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-20798 being exploited?

There is no known exploitation of CVE-2018-20798 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2019-16915](https://insights.sbomify.com/CVE-2019-16915/): Path traversal in n/a (critical 9.8)
- [CVE-2020-21487](https://insights.sbomify.com/CVE-2020-21487/): Cross-site scripting in n/a (critical 9.6)
- [CVE-2024-46538](https://insights.sbomify.com/CVE-2024-46538/): Cross-site scripting in n/a (critical 9.3)
- [CVE-2023-48123](https://insights.sbomify.com/CVE-2023-48123/): Command injection in n/a (high 8.8)
- [CVE-2023-42326](https://insights.sbomify.com/CVE-2023-42326/): Command injection in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-20798 and fix it if it is affected.

What it is: CVE-2018-20798 is a high-severity vulnerability in n/a, published on 1 Mar 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-2018-20798 in the wild and no public exploit code.

Affected product: n/a. 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-2018-20798/ (Markdown: https://insights.sbomify.com/CVE-2018-20798/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-20798
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-20798
- OSV: https://osv.dev/vulnerability/CVE-2018-20798

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-20798/
Summaries are generated and may contain mistakes; the official description above is the record.