# CVE-2019-18792: Security feature bypass in n/a

> Attackers can bypass TCP-based signatures in Suricata by injecting fake FIN packets, allowing malicious traffic to evade detection.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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:** Yes
- **Published:** 6 Jan 2020
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2019-18792, GHSA-p4hg-mvq8-47jj, UBUNTU-CVE-2019-18792

## What is CVE-2019-18792?

CVE-2019-18792 is a critical vulnerability in Debian Debian Linux, published on 6 Jan 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in Suricata 5.0.0. It is possible to bypass/evade any tcp based signature by overlapping a TCP segment with a fake FIN packet. The fake FIN packet is injected just before the PUSH ACK packet we want to bypass. The PUSH ACK packet (containing the data) will be ignored by Suricata because it overlaps the FIN packet (the sequence and ack number are identical in the two packets). The client will ignore the fake FIN packet because the ACK flag is not set. Both linux and windows clients are ignoring the injected packet.

Weakness: CWE-436 (Interpretation Conflict)

## Which versions are affected by CVE-2019-18792?

It affects 2 products.


Products: Debian Debian Linux, Oisf Suricata.

## How do I fix CVE-2019-18792?

Upgrade to a fixed version.

## Is CVE-2019-18792 being exploited?

There is no known exploitation of CVE-2019-18792 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-18792 and fix it if it is affected.

What it is: CVE-2019-18792 is a critical vulnerability in Debian Debian Linux, published on 6 Jan 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-2019-18792 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2019-18792/ (Markdown: https://insights.sbomify.com/CVE-2019-18792/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-18792
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-18792
- OSV: https://osv.dev/vulnerability/CVE-2019-18792

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-18792/
Summaries are generated and may contain mistakes; the official description above is the record.