Apache · HTTP Server
CVE-2021-41773
Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49
What it is
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.
CISA: 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.
What to do
Apply updates per vendor instructions.
Deadline for US federal agencies: November 17, 2021
- Added to the CISA list
- November 3, 2021
- Published
- October 5, 2021
- Severity
- High 7.5 CVSS 3.1
- Chance of attacks in the next 30 days (EPSS)
- >99.9% in the top 0.1% of all known vulnerabilities
- Weakness
- CWE-22
- More details
- NVD · CVE.org · CISA
All references (20)
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-pathtrv-LAzg68cZ
- https://httpd.apache.org/security/vulnerabilities_24.html
- https://lists.apache.org/thread.html/r6abf5f2ba6f1aa8b1030f95367aaf17660c4e4c78cb2338aee18982f%40%3Cusers.htt…
- https://lists.apache.org/thread.html/r98d704ed4377ed889d40479db79ed1ee2f43b2ebdd79ce84b042df45%40%3Cannounce.…
- http://www.openwall.com/lists/oss-security/2021/10/05/2
- http://www.openwall.com/lists/oss-security/2021/10/07/1
- https://lists.apache.org/thread.html/r7c795cd45a3384d4d27e57618a215b0ed19cb6ca8eb070061ad5d837%40%3Cannounce.…
- https://lists.apache.org/thread.html/rb5b0e46f179f60b0c70204656bc52fcb558e961cb4d06a971e9e3efb%40%3Cusers.htt…
- http://www.openwall.com/lists/oss-security/2021/10/07/6
- http://www.openwall.com/lists/oss-security/2021/10/08/1
- https://lists.apache.org/thread.html/r17a4c6ce9aff662efd9459e9d1850ab4a611cb23392fc68264c72cb3%40%3Ccvs.httpd…
- http://www.openwall.com/lists/oss-security/2021/10/08/2
- http://www.openwall.com/lists/oss-security/2021/10/08/3
- http://www.openwall.com/lists/oss-security/2021/10/08/4
- http://www.openwall.com/lists/oss-security/2021/10/08/6
- http://www.openwall.com/lists/oss-security/2021/10/08/5
- http://www.openwall.com/lists/oss-security/2021/10/09/1
- http://packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal.html
- http://packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal-Remote-Code-Execution.ht…
- http://www.openwall.com/lists/oss-security/2021/10/11/4
More exploited flaws from Apache
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| May 1, 2025 | Improper Escaping of Output | HTTP Server | Critical 9.1 | >99.9% |
| Nov 3, 2021 | Privilege Escalation | HTTP Server | High 7.8 | 65% |
| Nov 3, 2021 | Path Traversal | HTTP Server | Critical 9.8 | >99.9% |
| Oct 8, 2026 | Command Injection | Struts | High 8.1 | 97% |
| Aug 4, 2026 | Missing Encryption of Sensitive Data | Tomcat | High 7.5 | 99% |
| Apr 16, 2026 | Improper Input Validation | ActiveMQ | High 8.8 | 98% |
| Apr 1, 2025 | Path Equivalence | Tomcat | Critical 10.0 | 99.9% |
| Feb 4, 2025 | Forced Browsing | OFBiz | Critical 9.8 | >99.9% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.