# CVE-2020-35863: HTTP Request Smuggling in hyper

> Attackers can exploit HTTP request smuggling in the hyper crate to achieve remote code execution on loopback servers.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:** 31 Dec 2020
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-35863, GHSA-h3qr-rq2j-74w4, RUSTSEC-2020-0008

## What is CVE-2020-35863?

CVE-2020-35863 is a critical vulnerability in n/a, published on 31 Dec 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in the hyper crate before 0.12.34 for Rust. HTTP request smuggling can occur. Remote code execution can occur in certain situations with an HTTP server on the loopback interface.

Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests)

## Which versions are affected by CVE-2020-35863?

3 open source packages ship an affected version, including hyper. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hyper` | crates.io | From 0.11.0 | 0.12.34 |
| `hyper` | crates.io | From 0.11.0 | 0.12.34 |
| `hyper` | crates.io | From 0.11.0 | 0.12.34 |

Products: Hyper Hyper.

## How do I fix CVE-2020-35863?

Upgrade hyper to 0.12.34 or later.

## Is CVE-2020-35863 being exploited?

There is no known exploitation of CVE-2020-35863 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2022-31394](https://insights.sbomify.com/CVE-2022-31394/): Denial of service in n/a (high 7.5)
- [CVE-2021-32714](https://insights.sbomify.com/CVE-2021-32714/): Integer Overflow in Chunked Transfer-Encoding (medium 5.9)
- [CVE-2017-18587](https://insights.sbomify.com/CVE-2017-18587/): Headers containing newline characters can split messages in hyper (medium 5.3)
- [CVE-2021-21299](https://insights.sbomify.com/CVE-2021-21299/): Multiple Transfer-Encoding headers misinterprets request payload (medium 4.8)
- [CVE-2016-10932](https://insights.sbomify.com/CVE-2016-10932/): HTTPS MitM vulnerability due to lack of hostname verification (medium 4.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-35863 and fix it if it is affected.

What it is: CVE-2020-35863 is a critical vulnerability in n/a, published on 31 Dec 2020. 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-2020-35863 in the wild and no public exploit code.

Affected packages and fixed versions:
- hyper (crates.io): affected from 0.11.0; fixed in 0.12.34
- hyper (crates.io): affected from 0.11.0; fixed in 0.12.34
- hyper (crates.io): affected from 0.11.0; fixed in 0.12.34

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-2020-35863/ (Markdown: https://insights.sbomify.com/CVE-2020-35863/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-35863
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-35863
- OSV: https://osv.dev/vulnerability/CVE-2020-35863

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-35863/
Summaries are generated and may contain mistakes; the official description above is the record.