CVEs / CVE-2021-42013

CVE-2021-42013: 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. This CVE ID resolves an incomplete patch for CVE-2021-41773.

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.

Affected and fixed versions

Exploitation

Severity

References

• CVE-2021-42013 on NVD
• CVE-2021-42013 in the CISA KEV catalog
• CVE-2021-42013 on OSV
• http://jvn.jp/en/jp/JVN51106450/index.html Third Party Advisory
• http://packetstormsecurity.com/files/164501/Apache-HTTP-Server-2.4.50-Path-Traversal-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
• http://packetstormsecurity.com/files/164609/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.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://packetstormsecurity.com/files/165089/Apache-HTTP-Server-2.4.50-CVE-2021-42013-Exploitation.html Third Party Advisory, VDB Entry
• http://packetstormsecurity.com/files/167397/Apache-2.4.50-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
• 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 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 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, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/10/15/3 Mailing List, 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