Not rated Exploited · ransomware

CVE-2021-41773 Apache HTTP Server Path Traversal Vulnerability

Active exploitation observed

· CISA KEV catalogue

Required action Apply updates per vendor instructions.

Ransomware campaigns Known to be used

Weakness CWE-22

Description

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 and versions

Product	Affected versions	Fixed in
Apache HTTP Server	Versions not published

References

httpd.apache.org httpd.apache.org
[httpd-users] 20211005 [users@httpd] CVE-2021-41773: Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49 lists.apache.org
[announce] 20211005 CVE-2021-41773: Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49 lists.apache.org
[oss-security] 20211005 CVE-2021-41773: Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49 www.openwall.com
[oss-security] 20211007 RE: CVE-2021-41773: Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49 www.openwall.com
[announce] 20211007 CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) lists.apache.org
[httpd-users] 20211007 [users@httpd] CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) lists.apache.org
[oss-security] 20211007 CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
20211007 Apache HTTP Server Vulnerabilties: October 2021 tools.cisco.com
[oss-security] 20211008 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
[httpd-cvs] 20211008 [httpd-site] branch main updated: * Align with CVE-2021-42013 based on the latest findings lists.apache.org
[oss-security] 20211008 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
[oss-security] 20211008 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
[oss-security] 20211008 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
[oss-security] 20211008 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
[oss-security] 20211008 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
[oss-security] 20211009 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
packetstormsecurity.com packetstormsecurity.com
packetstormsecurity.com packetstormsecurity.com
[oss-security] 20211011 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
FEDORA-2021-2a10bc68a4 lists.fedoraproject.org
FEDORA-2021-aaf90ef84a lists.fedoraproject.org
[oss-security] 20211015 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
[oss-security] 20211016 Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) www.openwall.com
www.oracle.com www.oracle.com
security.netapp.com security.netapp.com
packetstormsecurity.com packetstormsecurity.com
packetstormsecurity.com packetstormsecurity.com
GLSA-202208-20 security.gentoo.org

Timeline

Published October 5, 2021
Added to the KEV catalogue November 3, 2021
Last modified October 21, 2025

The 139 CVEs of Apache HTTP Server →

CVE-2026-63686 A NULL pointer dereference in mod_xml2enc in Apache Software Foundation Apache HTTP Server before 2.4.69 on all… Not rated CVE-2026-93546 Integer overflow in mod_dav_fs in Apache HTTP Server through 2.4.68 allows an authenticated WebDAV client with write… Not rated CVE-2026-79768 Path equivalence: '/./' (single dot directory) vulnerability in Apache HTTP Server's mod_userdir module when… Not rated CVE-2026-73637 Use after free in mod_auth_digest in Apache Software Foundation Apache HTTP Server before 2.4.69 on all platforms allows… Not rated

Track this CVE