# CVE-2019-18838: Null dereference in n/a

> A malformed HTTP request without a Host header can cause a NULL pointer dereference in Envoy, leading to process termination and denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 13 Dec 2019
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-f2rv-4w6x-rwhc, GHSA-m3j5-qf4q-m73w

## What is CVE-2019-18838?

CVE-2019-18838 is a high-severity vulnerability in Envoyproxy Envoy, published on 13 Dec 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in Envoy 1.12.0. Upon receipt of a malformed HTTP request without a Host header, it sends an internally generated "Invalid request" response. This internally generated response is dispatched through the configured encoder filter chain before being sent to the client. An encoder filter that invokes route manager APIs that access a request's Host header causes a NULL pointer dereference, resulting in abnormal termination of the Envoy process.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2019-18838?

It affects 1 product.


Products: Envoyproxy Envoy.

## How do I fix CVE-2019-18838?

Upgrade to a fixed version.

## Is CVE-2019-18838 being exploited?

There is no known exploitation of CVE-2019-18838 in the wild and no public exploit code.

## Other vulnerabilities in Envoyproxy Envoy

- [CVE-2022-29226](https://insights.sbomify.com/CVE-2022-29226/): Trivial authentication bypass in Envoy (critical 10.0)
- [CVE-2019-18801](https://insights.sbomify.com/CVE-2019-18801/): Memory corruption in n/a (critical 9.8)
- [CVE-2019-18802](https://insights.sbomify.com/CVE-2019-18802/): Security feature bypass in n/a (critical 9.8)
- [CVE-2020-35470](https://insights.sbomify.com/CVE-2020-35470/): Information disclosure in n/a (high 8.8)
- [CVE-2024-23324](https://insights.sbomify.com/CVE-2024-23324/): Envoy ext auth can be bypassed when Proxy protocol filter sets invalid UTF-8 metadata (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-18838 and fix it if it is affected.

What it is: CVE-2019-18838 is a high-severity vulnerability in Envoyproxy Envoy, published on 13 Dec 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-2019-18838 in the wild and no public exploit code.

Affected product: Envoyproxy Envoy. 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-2019-18838/ (Markdown: https://insights.sbomify.com/CVE-2019-18838/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-18838
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-18838
- OSV: https://osv.dev/vulnerability/CVE-2019-18838

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-18838/
Summaries are generated and may contain mistakes; the official description above is the record.