# CVE-2019-9518: Some HTTP/2 implementations are vulnerable to a flood of empty frames, potentially leading to a denial of service

> Attackers can cause denial of service by flooding HTTP/2 servers with empty frames, consuming excessive CPU resources.

- **Severity:** High 7.5 (`CVSS:3.0/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 Aug 2019
- **Updated:** 4 Aug 2024
- **Also known as:** ALPINE-CVE-2019-9518, CLEANSTART-2026-BZ30025, CLEANSTART-2026-WZ77365, CVE-2019-14992, DEBIAN-CVE-2019-9518, GHSA-93p3-5r25-4p75, UBUNTU-CVE-2019-9518

## What is CVE-2019-9518?

CVE-2019-9518 is a high-severity denial of service vulnerability in Apache Traffic Server, published on 13 Aug 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Some HTTP/2 implementations are vulnerable to a flood of empty frames, potentially leading to a denial of service. The attacker sends a stream of frames with an empty payload and without the end-of-stream flag. These frames can be DATA, HEADERS, CONTINUATION and/or PUSH_PROMISE. The peer spends time processing each frame disproportionate to attack bandwidth. This can consume excess CPU.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2019-9518?

It affects 18 products.


Products: Apache Traffic Server, Apple Swiftnio, Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Mcafee Web Gateway, Nodejs Node.js, Opensuse Leap, Oracle Graalvm, Redhat Enterprise Linux, Redhat Jboss Core Services, Redhat Jboss Enterprise Application Platform, Redhat Openshift Service Mesh, Redhat Quay, Redhat Software Collections, Synology Diskstation Manager, Synology Skynas, Synology Vs960hd Firmware.

## How do I fix CVE-2019-9518?

Apply the vendor's patch.

## Is CVE-2019-9518 being exploited?

There is no known exploitation of CVE-2019-9518 in the wild and no public exploit code.

## Other vulnerabilities in Apache Traffic Server

- [CVE-2014-3525](https://insights.sbomify.com/CVE-2014-3525/): Other in n/a (critical 10.0)
- [CVE-2021-43082](https://insights.sbomify.com/CVE-2021-43082/): heap-buffer-overflow with stats-over-http plugin (critical 9.8)
- [CVE-2021-35474](https://insights.sbomify.com/CVE-2021-35474/): Dynamic stack buffer overflow in cachekey plugin (critical 9.8)
- [CVE-2019-17559](https://insights.sbomify.com/CVE-2019-17559/): Other in Apache Traffic Server (critical 9.8)
- [CVE-2019-17565](https://insights.sbomify.com/CVE-2019-17565/): Other in Apache Traffic Server (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-9518 and fix it if it is affected.

What it is: CVE-2019-9518 is a high-severity denial of service vulnerability in Apache Traffic Server, published on 13 Aug 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-2019-9518 in the wild and no public exploit code.

Affected product: Apache Traffic Server. 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-2019-9518/ (Markdown: https://insights.sbomify.com/CVE-2019-9518/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-9518
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-9518
- OSV: https://osv.dev/vulnerability/CVE-2019-9518

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-9518/
Summaries are generated and may contain mistakes; the official description above is the record.