# CVE-2020-27631: Weak cryptography in n/a

> Improper randomization of TCP Initial Sequence Numbers in CycloneTCP allows attackers to bypass security controls.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Oct 2023
- **Updated:** 19 Sep 2024
- **Also known as:** GHSA-gvwh-h9wm-jvg4

## What is CVE-2020-27631?

CVE-2020-27631 is a critical vulnerability in n/a, published on 10 Oct 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In Oryx CycloneTCP 1.9.6, TCP ISNs are improperly random.

Weakness: CWE-330 (Use of Insufficiently Random Values)

## Which versions are affected by CVE-2020-27631?

It affects 1 product.


Products: Oryx-Embedded Cyclonetcp.

## How do I fix CVE-2020-27631?

No fix has been published for CVE-2020-27631 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-27631 being exploited?

There is no known exploitation of CVE-2020-27631 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-26788](https://insights.sbomify.com/CVE-2021-26788/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-27631 and fix it if it is affected.

What it is: CVE-2020-27631 is a critical vulnerability in n/a, published on 10 Oct 2023. 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-2020-27631 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-2020-27631/ (Markdown: https://insights.sbomify.com/CVE-2020-27631/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-27631
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-27631
- OSV: https://osv.dev/vulnerability/CVE-2020-27631

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-27631/
Summaries are generated and may contain mistakes; the official description above is the record.