# CVE-2019-18836: Denial of service in n/a

> Remote attackers can cause denial of service via infinite busy loops in Envoy proxy when specific timeout settings are enabled.

- **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:** No
- **Published:** 11 Nov 2019
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-3xvf-4396-cj46, GHSA-4r53-8549-7m3r

## What is CVE-2019-18836?

CVE-2019-18836 is a high-severity denial of service vulnerability in Envoyproxy Envoy, published on 11 Nov 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Envoy 1.12.0 allows a remote denial of service because of resource loops, as demonstrated by a single idle TCP connection being able to keep a worker thread in an infinite busy loop when continue_on_listener_filters_timeout is used."

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2019-18836?

It affects 2 products.


Products: Envoyproxy Envoy, Istio Istio.

## How do I fix CVE-2019-18836?

No fix has been published for CVE-2019-18836 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-18836 being exploited?

There is no known exploitation of CVE-2019-18836 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-2019-18836 and fix it if it is affected.

What it is: CVE-2019-18836 is a high-severity denial of service vulnerability in Envoyproxy Envoy, published on 11 Nov 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-2019-18836 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-2019-18836/ (Markdown: https://insights.sbomify.com/CVE-2019-18836/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-18836
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-18836
- OSV: https://osv.dev/vulnerability/CVE-2019-18836

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-18836/
Summaries are generated and may contain mistakes; the official description above is the record.