CVE-2021-41773: Apache HTTP Server Path Traversal Vulnerability

Critical severity, CVSS 9.8. Actively exploited: in CISA KEV since 2021-11-03. EPSS: 100% chance of exploitation in the next 30 days.

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.

Affected products

• Apache HTTP Server: version 2.4.49 only
• Fedoraproject Fedora: version 34 only; version 35 only
• Netapp Cloud Backup: affected versions not specified
• Oracle Instantis Enterprisetrack: version 17.1 only; version 17.2 only; version 17.3 only

Published 2021-10-05. Last modified 2026-06-17.