# CVE-2011-3639: The mod_proxy module in the Apache HTTP Server 2.0.x through 2.0.64 and 2.2.x before 2.2.18, when the Revision 1179239 patch is in place, do


- **Severity:** Medium 4.3 (`AV:N/AC:M/Au:N/C:N/I:P/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 30 Nov 2011
- **Updated:** 6 Aug 2024
- **Also known as:** DEBIAN-CVE-2011-3639, GHSA-rqg3-pfxx-wwq3

## What is CVE-2011-3639?

CVE-2011-3639 is a medium-severity vulnerability in Apache Http Server, published on 30 Nov 2011. 

### Official description

The mod_proxy module in the Apache HTTP Server 2.0.x through 2.0.64 and 2.2.x before 2.2.18, when the Revision 1179239 patch is in place, does not properly interact with use of (1) RewriteRule and (2) ProxyPassMatch pattern matches for configuration of a reverse proxy, which allows remote attackers to send requests to intranet servers by using the HTTP/0.9 protocol with a malformed URI containing an initial @ (at sign) character.  NOTE: this vulnerability exists because of an incomplete fix for CVE-2011-3368.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2011-3639?

It affects 10 products.


Products: Apache Http Server, Apache Http Server2.0a1, Apache Http Server2.0a2, Apache Http Server2.0a3, Apache Http Server2.0a4, Apache Http Server2.0a5, Apache Http Server2.0a6, Apache Http Server2.0a7, Apache Http Server2.0a8, Apache Http Server2.0a9.

## How do I fix CVE-2011-3639?

Upgrade to a fixed version.

## Is CVE-2011-3639 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2011-3639 exists.

Public exploit code:

- Apache 2.2.15 mod_proxy - Reverse Proxy Security Bypass (exploitdb)

## Other vulnerabilities in Apache Http Server

- [CVE-2021-42013](https://insights.sbomify.com/CVE-2021-42013/): Apache HTTP Server Path Traversal (critical 9.8, exploited in the wild)
- [CVE-2024-38475](https://insights.sbomify.com/CVE-2024-38475/): Apache HTTP Server Improper Escaping of Output (critical 9.1, exploited in the wild)
- [CVE-2021-40438](https://insights.sbomify.com/CVE-2021-40438/): Apache HTTP Server-Side Request Forgery (SSRF) (critical 9.0, exploited in the wild)
- [CVE-2019-0211](https://insights.sbomify.com/CVE-2019-0211/): Apache HTTP Server Privilege Escalation (high 7.8, exploited in the wild)
- [CVE-2021-41773](https://insights.sbomify.com/CVE-2021-41773/): Apache HTTP Server Path Traversal (high 7.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2011-3639 and fix it if it is affected.

What it is: CVE-2011-3639 is a medium-severity vulnerability in Apache Http Server, published on 30 Nov 2011. 
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2011-3639 exists.

Affected product: Apache Http 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-2011-3639/ (Markdown: https://insights.sbomify.com/CVE-2011-3639/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2011-3639
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2011-3639
- OSV: https://osv.dev/vulnerability/CVE-2011-3639

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From sbomify Insights: https://insights.sbomify.com/CVE-2011-3639/
Summaries are generated and may contain mistakes; the official description above is the record.