# CVE-2021-42013: Apache HTTP Server Path Traversal

> Attackers can exploit path traversal to read arbitrary files or execute code if CGI is enabled and default protections are bypassed.

- **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:** Yes, since 3 Nov 2021 (CISA KEV), used in ransomware
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Oct 2021
- **Updated:** 21 Oct 2025
- **Also known as:** ALPINE-CVE-2021-42013, BIT-apache-2021-42013, CLEANSTART-2026-XG20648, DEBIAN-CVE-2021-42013, GHSA-m24x-wx9p-jqmh, MGASA-2021-0470

## What is CVE-2021-42013?

CVE-2021-42013 is a critical path traversal vulnerability in Apache Http Server, published on 7 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

It was found that the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient. An attacker could use a path traversal attack to map URLs to files outside the directories configured by Alias-like directives. If files outside of these directories are not protected by the usual default configuration "require all denied", these requests can succeed. If CGI scripts are also enabled for these aliased pathes, this could allow for remote code execution. This issue only affects Apache 2.4.49 and Apache 2.4.50 and not earlier versions.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2021-42013?

1 open source package ship an affected version, including apache. It affects 6 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `apache` | Bitnami | From 2.4.49 | 2.4.50, 2.4.51 |

Products: Apache Http Server, Fedoraproject Fedora, Netapp Cloud Backup, Oracle Instantis Enterprisetrack, Oracle Jd Edwards Enterpriseone Tools, Oracle Secure Backup.

## How do I fix CVE-2021-42013?

Upgrade apache to a fixed version for your release line: 2.4.50 or 2.4.51. US federal agencies must fix it by 17 Nov 2021.

## Is CVE-2021-42013 being exploited?

Yes. Attackers have exploited CVE-2021-42013 in the wild since at least 3 Nov 2021, including in ransomware campaigns.

Public exploit code:

- cve-2021-42013.py is a python script that will help in finding Path Traversal or Remote Code Execution vulnerability in Apache 2.4.50 (github_poc): https://github.com/walnutsecurity/cve-2021-42013
- Apache 2.4.50 Path traversal vulnerability (github_poc): https://github.com/Vulnmachines/cve-2021-42013
- Apache 远程代码执行 （CVE-2021-42013）批量检测工具：Apache HTTP Server是美国阿帕奇（Apache）基金会的一款开源网页服务器。该服务器具有快速、可靠且可通过简单的API进行扩充的特点，发现 Apache HTTP Server 2.4.50 中针对 CVE-2021-41773 的修复不够充分。攻击者可以使用路径遍历攻击将 URL 映射到由类似别名的指令配置的目录之外的文件。如果这些目录之外的文件不受通常的默认配置“要求全部拒绝”的保护，则这些请求可能会成功。如果还为这些别名路径启用了 CGI 脚本，则这可能允许远程代码执行。此问题仅影响 Apache 2.4.49 和 Apache 2.4.50，而不影响更早版本。 (github_poc): https://github.com/asaotomo/CVE-2021-42013-Apache-RCE-Poc-Exp
- Exploit with  integrated shodan search (github_poc): https://github.com/andrea-mattioli/apache-exploit-CVE-2021-42013
- PoC CVE-2021-42013 reverse shell Apache 2.4.50 with CGI (github_poc): https://github.com/TheLastVvV/CVE-2021-42013_Reverse-Shell
- CVE-2021-42013 Vulnerability Scanner  This Python script checks for the Remote Code Execution (RCE) vulnerability (CVE-2021-42013) in Apache 2.4.50.  (github_poc): https://github.com/BassoNicolas/CVE-2021-42013

## Other vulnerabilities in Apache Http Server

- [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)
- [CVE-2010-0425](https://insights.sbomify.com/CVE-2010-0425/): Use after free in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-42013 and fix it if it is affected.

What it is: CVE-2021-42013 is a critical path traversal vulnerability in Apache Http Server, published on 7 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2021-42013 in the wild since at least 3 Nov 2021, including in ransomware campaigns.

Affected packages and fixed versions:
- apache (Bitnami): affected from 2.4.49; fixed in 2.4.50, 2.4.51

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-2021-42013/ (Markdown: https://insights.sbomify.com/CVE-2021-42013/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-42013
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-42013
- OSV: https://osv.dev/vulnerability/CVE-2021-42013

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-42013/
Summaries are generated and may contain mistakes; the official description above is the record.