# CVE-2013-4366: Hostname verification in Apache HttpClient 4.3 was disabled by default

> Attackers can bypass hostname verification in Apache HttpClient due to a missing null check, potentially enabling man-in-the-middle attacks.

- **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:** 30 Oct 2017
- **Updated:** 6 Aug 2024
- **Also known as:** DEBIAN-CVE-2013-4366, GHSA-pqwh-44jj-p5rm

## What is CVE-2013-4366?

CVE-2013-4366 is a critical vulnerability in n/a, published on 30 Oct 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

http/impl/client/HttpClientBuilder.java in Apache HttpClient 4.3.x before 4.3.1 does not ensure that X509HostnameVerifier is not null, which allows attackers to have unspecified impact via vectors involving hostname verification.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2013-4366?

2 open source packages ship an affected version, including org.apache.httpcomponents:httpclient. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.apache.httpcomponents:httpclient` | Maven | From 4.3 | 4.3.1 |
| `org.apache.httpcomponents:httpclient` | Maven | From 4.3 | 4.3.1 |

Products: Apache Httpclient.

## How do I fix CVE-2013-4366?

Upgrade org.apache.httpcomponents:httpclient to 4.3.1 or later.

## Is CVE-2013-4366 being exploited?

There is no known exploitation of CVE-2013-4366 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2026-71290](https://insights.sbomify.com/CVE-2026-71290/): Apache HttpComponents Client: TLS hostname verification silently disabled on the async transport (default config, MITM) (critical 9.1)
- [CVE-2025-27820](https://insights.sbomify.com/CVE-2025-27820/): Apache HttpComponents: PSL (Public Suffix List) validation bypass (high 7.5)
- [CVE-2026-40542](https://insights.sbomify.com/CVE-2026-40542/): Apache HttpClient accepts SCRAM-SHA-256 authentication without proper mutual authentication verification (high 7.3)
- [CVE-2012-5783](https://insights.sbomify.com/CVE-2012-5783/): Improper Certificate Validation in Apache Commons HttpClient (medium 5.8)
- [CVE-2026-64607](https://insights.sbomify.com/CVE-2026-64607/): Apache HttpComponents Client: Connection Leak on Content-Encoding Decode Error Leads to Pool Exhaustion DoS (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2013-4366 and fix it if it is affected.

What it is: CVE-2013-4366 is a critical vulnerability in n/a, published on 30 Oct 2017. 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-2013-4366 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.apache.httpcomponents:httpclient (Maven): affected from 4.3; fixed in 4.3.1
- org.apache.httpcomponents:httpclient (Maven): affected from 4.3; fixed in 4.3.1

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-2013-4366/ (Markdown: https://insights.sbomify.com/CVE-2013-4366/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2013-4366
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2013-4366
- OSV: https://osv.dev/vulnerability/CVE-2013-4366

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From sbomify Insights: https://insights.sbomify.com/CVE-2013-4366/
Summaries are generated and may contain mistakes; the official description above is the record.