# CVE-2020-15811: Other in n/a

> Attackers can perform HTTP request splitting to poison caches and bypass security controls in Squid proxy servers.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Sep 2020
- **Updated:** 4 Aug 2024
- **Also known as:** ALPINE-CVE-2020-15811, DEBIAN-CVE-2020-15811, GHSA-c7p8-xqhm-49wv, UBUNTU-CVE-2020-15811

## What is CVE-2020-15811?

CVE-2020-15811 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 2 Sep 2020. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the browser cache and any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any downstream caches.

Weakness: CWE-697 (Incorrect Comparison)

## Which versions are affected by CVE-2020-15811?

It affects 5 products.


Products: Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Opensuse Leap, Squid-Cache Squid.

## How do I fix CVE-2020-15811?

Upgrade to a fixed version.

## Is CVE-2020-15811 being exploited?

There is no known exploitation of CVE-2020-15811 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-15811 and fix it if it is affected.

What it is: CVE-2020-15811 is a medium-severity vulnerability in Canonical Ubuntu Linux, published on 2 Sep 2020. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-15811 in the wild and no public exploit code.

Affected product: Canonical Ubuntu Linux. 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-2020-15811/ (Markdown: https://insights.sbomify.com/CVE-2020-15811/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-15811
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-15811
- OSV: https://osv.dev/vulnerability/CVE-2020-15811

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-15811/
Summaries are generated and may contain mistakes; the official description above is the record.