# CVE-2021-27737: Denial of service in Apache Traffic Server

> Remote attackers can cause a denial of service in Apache Traffic Server via the experimental Slicer plugin.

- **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:** 14 May 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-j9pm-x686-vcvp

## What is CVE-2021-27737?

CVE-2021-27737 is a high-severity denial of service vulnerability in Apache Traffic Server, published on 14 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Apache Traffic Server 9.0.0 is vulnerable to a remote DOS attack on the experimental Slicer plugin.

## Which versions are affected by CVE-2021-27737?

It affects 1 product.


Products: Apache Traffic Server.

## How do I fix CVE-2021-27737?

No fix has been published for CVE-2021-27737 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-27737 being exploited?

There is no known exploitation of CVE-2021-27737 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-2021-27737 and fix it if it is affected.

What it is: CVE-2021-27737 is a high-severity denial of service vulnerability in Apache Traffic Server, published on 14 May 2021. 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-2021-27737 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-2021-27737/ (Markdown: https://insights.sbomify.com/CVE-2021-27737/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27737
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27737
- OSV: https://osv.dev/vulnerability/CVE-2021-27737

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27737/
Summaries are generated and may contain mistakes; the official description above is the record.