CVEs / CVE-2021-41773

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

• Known exploited in the CISA KEV catalog since 3 Nov 2021
• critical 9.8 CVSS 3.1 (NVD)
• EPSS 99.9% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
• Last changed at its sources 24 Oct 2026

Summary

Apache HTTP Server contains a path traversal vulnerability that allows an attacker to perform remote code execution if files outside directories configured by Alias-like directives are not under default �require all denied� or if CGI scripts are enabled. The original patch issued under this CVE ID is insufficient, please review remediation information under CVE-2021-42013.

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 and fixed versions

Exploitation

Severity

References

• CVE-2021-41773 on NVD
• CVE-2021-41773 in the CISA KEV catalog
• CVE-2021-41773 on OSV
• http://packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
• http://packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal.html Exploit, Third Party Advisory, VDB Entry
• http://packetstormsecurity.com/files/164629/Apache-2.4.49-2.4.50-Traversal-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
• http://packetstormsecurity.com/files/164941/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
• http://www.openwall.com/lists/oss-security/2021/10/05/2 Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/07/1 Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/07/6 Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/08/1 Exploit, Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/08/2 Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/08/3 Exploit, Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/08/4 Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/08/5 Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/08/6 Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/09/1 Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/11/4 Mailing List, Patch, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/15/3 Mailing List, Patch, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/16/1 Mailing List, Third Party Advisory
• https://httpd.apache.org/security/vulnerabilities_24.html Release Notes, Vendor Advisory
• https://lists.apache.org/thread.html/r17a4c6ce9aff662efd9459e9d1850ab4a611cb23392fc68264c72cb3%40%3Ccvs.httpd.apache.org%3E Mailing List, Patch
• https://lists.apache.org/thread.html/r6abf5f2ba6f1aa8b1030f95367aaf17660c4e4c78cb2338aee18982f%40%3Cusers.httpd.apache.org%3E Mailing List