# CVE-2019-15226: Denial of service in n/a

> Remote attackers can cause CPU exhaustion and denial of service in Envoy proxy by sending requests with many small headers due to inefficient header size validation.

- **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:** 9 Oct 2019
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-cggr-h689-7v7x

## What is CVE-2019-15226?

CVE-2019-15226 is a high-severity denial of service vulnerability in Envoyproxy Envoy, published on 9 Oct 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the headers stays below a maximum limit. The implementation in versions 1.10.0 through 1.11.1 for HTTP/1.x traffic and all versions of Envoy for HTTP/2 traffic had O(n^2) performance characteristics. A remote attacker may craft a request that stays below the maximum request header size but consists of many thousands of small headers to consume CPU and result in a denial-of-service attack.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2019-15226?

It affects 1 product.


Products: Envoyproxy Envoy.

## How do I fix CVE-2019-15226?

No fix has been published for CVE-2019-15226 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-15226 being exploited?

There is no known exploitation of CVE-2019-15226 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-2019-15226 and fix it if it is affected.

What it is: CVE-2019-15226 is a high-severity denial of service vulnerability in Envoyproxy Envoy, published on 9 Oct 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-2019-15226 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-2019-15226/ (Markdown: https://insights.sbomify.com/CVE-2019-15226/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-15226
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-15226
- OSV: https://osv.dev/vulnerability/CVE-2019-15226

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-15226/
Summaries are generated and may contain mistakes; the official description above is the record.