CVE-2021-41773
Apache Software Foundation Apache HTTP Server
Published 5 Oct 2021 · updated 17 Jun 2026 · Analyzed
Exploited in the wild
CISA added this to its Known Exploited Vulnerabilities catalog on 3 Nov 2021, with a remediation deadline of 17 Nov 2021 for US federal agencies. It has been used in ransomware campaigns.
Required action: Apply updates per vendor instructions.
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.
References
- packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal-Remote-Code-Execution.html · Exploit, Third Party Advisory, VDB Entry
- packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal.html · Exploit, Third Party Advisory, VDB Entry
- packetstormsecurity.com/files/164629/Apache-2.4.49-2.4.50-Traversal-Remote-Code-Execution.html · Exploit, Third Party Advisory, VDB Entry
- packetstormsecurity.com/files/164941/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.html · Exploit, Third Party Advisory, VDB Entry
- www.openwall.com/lists/oss-security/2021/10/05/2 · Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/07/1 · Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/07/6 · Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/08/1 · Exploit, Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/08/2 · Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/08/3 · Exploit, Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/08/4 · Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/08/5 · Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/08/6 · Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/09/1 · Mailing List, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/11/4 · Mailing List, Patch, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/15/3 · Mailing List, Patch, Third Party Advisory
- www.openwall.com/lists/oss-security/2021/10/16/1 · Mailing List, Third Party Advisory
- httpd.apache.org/security/vulnerabilities_24.html · Release Notes, Vendor Advisory
- lists.apache.org/thread.html/r17a4c6ce9aff662efd9459e9d1850ab4a611cb23392fc68264c72cb3%40%3Ccvs.httpd.apache.org%3E · Mailing List, Patch
- lists.apache.org/thread.html/r6abf5f2ba6f1aa8b1030f95367aaf17660c4e4c78cb2338aee18982f%40%3Cusers.httpd.apache.org%3E · Mailing List
- lists.apache.org/thread.html/r7c795cd45a3384d4d27e57618a215b0ed19cb6ca8eb070061ad5d837%40%3Cannounce.apache.org%3E · Mailing List
- lists.apache.org/thread.html/r98d704ed4377ed889d40479db79ed1ee2f43b2ebdd79ce84b042df45%40%3Cannounce.apache.org%3E · Mailing List
- lists.apache.org/thread.html/rb5b0e46f179f60b0c70204656bc52fcb558e961cb4d06a971e9e3efb%40%3Cusers.httpd.apache.org%3E · Mailing List
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RMIIEFINL6FUIOPD2A3M5XC6DH45Y3CC/ · Release Notes
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WS5RVHOIIRECG65ZBTZY7IEJVWQSQPG3/ · Release Notes