---
id: "CVE-2021-41773"
kind: "vulnerability"
aliases: ["CVE-2021-41773"]
title: "Apache HTTP Server: Apache HTTP Server Path Traversal Vulnerability"
severity: "critical"
cvss: 9.8
epss: 0.99992
exploited: true
status: "open"
category: "runtime"
products: [{"name": "Apache HTTP Server", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["apache-httpd", "exploited", "linux", "ransomware", "runtime", "self-hosted"]
not_affected_if: ["default-config", "managed-hosting"]
published_at: "2021-10-05T09:15:07+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-41773", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-41773", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-41773", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Apache HTTP Server: Apache HTTP Server Path Traversal Vulnerability

Apache HTTP Server 2.4.49 allows path traversal through crafted URLs, letting remote attackers read files outside the web root. If CGI scripts are enabled, the flaw can lead to remote code execution on the server.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Apache HTTP Server affected ? fixed ?

## How to check

Run httpd -v and check whether the version is 2.4.49.
Check whether CGI is enabled, for example with grep -rn 'ScriptAlias\|mod_cgi' on the Apache config directory.

## Fix

Upgrade Apache HTTP Server to a fixed release; this CVE's original patch was insufficient, so follow CVE-2021-42013 for the complete fix.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-41773
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2021-41773
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-41773

## From the sources

A flaw was found in a change made to path normalization in Apache HTTP Server 2.4.49. 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 is known to be exploited in the wild. This issue only affects Apache 2.4.49 and not earlier versions. The fix in Apache HTTP Server 2.4.50 was found to be incomplete, see CVE-2021-42013.

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