CVE-2021-41773

Name: CVE-2021-41773
Creator: NVD / NIST
Published: 2021-10-05T09:15:07.593+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10Actively ExploitedEPSS 99.99%

Last modified Jun 17, 2026

CVE-2021-41773 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. CISA has confirmed active exploitation in the wild. EPSS estimates a 99.99% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

99.99%

100.0th percentile

Probability of exploitation in the next 30 days. Learn more

Exploitation Status

This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by Nov 17, 2021.

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Apache	Http Server	2.4.49
Fedoraproject	Fedora	34
Fedoraproject	Fedora	35
Oracle	Instantis Enterprisetrack	17.1
Oracle	Instantis Enterprisetrack	17.2
Oracle	Instantis Enterprisetrack	17.3
Netapp	Cloud Backup	All versions

References

http://packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal.htmlExploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/164629/Apache-2.4.49-2.4.50-Traversal-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/164941/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
http://www.openwall.com/lists/oss-security/2021/10/05/2Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/07/1Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/07/6Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/1Exploit, Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/2Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/3Exploit, Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/4Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/5Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/6Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/09/1Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/11/4Mailing List, Patch, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/15/3Mailing List, Patch, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/16/1Mailing List, Third Party Advisory
https://httpd.apache.org/security/vulnerabilities_24.htmlRelease Notes, Vendor Advisory
https://lists.apache.org/thread.html/r17a4c6ce9aff662efd9459e9d1850ab4a611cb23392fc68264c72cb3%40%3Ccvs.httpd.apache.org%3EMailing List, Patch
https://lists.apache.org/thread.html/r6abf5f2ba6f1aa8b1030f95367aaf17660c4e4c78cb2338aee18982f%40%3Cusers.httpd.apache.org%3EMailing List
https://lists.apache.org/thread.html/r7c795cd45a3384d4d27e57618a215b0ed19cb6ca8eb070061ad5d837%40%3Cannounce.apache.org%3EMailing List
https://lists.apache.org/thread.html/r98d704ed4377ed889d40479db79ed1ee2f43b2ebdd79ce84b042df45%40%3Cannounce.apache.org%3EMailing List
https://lists.apache.org/thread.html/rb5b0e46f179f60b0c70204656bc52fcb558e961cb4d06a971e9e3efb%40%3Cusers.httpd.apache.org%3EMailing List
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RMIIEFINL6FUIOPD2A3M5XC6DH45Y3CC/Release Notes
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WS5RVHOIIRECG65ZBTZY7IEJVWQSQPG3/Release Notes
https://security.gentoo.org/glsa/202208-20Third Party Advisory
https://security.netapp.com/advisory/ntap-20211029-0009/Third Party Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-pathtrv-LAzg68cZThird Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.htmlPatch, Third Party Advisory
http://packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/164418/Apache-HTTP-Server-2.4.49-Path-Traversal.htmlExploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/164629/Apache-2.4.49-2.4.50-Traversal-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/164941/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
http://www.openwall.com/lists/oss-security/2021/10/05/2Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/07/1Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/07/6Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/1Exploit, Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/2Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/3Exploit, Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/4Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/5Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/08/6Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/09/1Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/11/4Mailing List, Patch, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/15/3Mailing List, Patch, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/10/16/1Mailing List, Third Party Advisory
https://httpd.apache.org/security/vulnerabilities_24.htmlRelease Notes, Vendor Advisory
https://lists.apache.org/thread.html/r17a4c6ce9aff662efd9459e9d1850ab4a611cb23392fc68264c72cb3%40%3Ccvs.httpd.apache.org%3EMailing List, Patch
https://lists.apache.org/thread.html/r6abf5f2ba6f1aa8b1030f95367aaf17660c4e4c78cb2338aee18982f%40%3Cusers.httpd.apache.org%3EMailing List
https://lists.apache.org/thread.html/r7c795cd45a3384d4d27e57618a215b0ed19cb6ca8eb070061ad5d837%40%3Cannounce.apache.org%3EMailing List
https://lists.apache.org/thread.html/r98d704ed4377ed889d40479db79ed1ee2f43b2ebdd79ce84b042df45%40%3Cannounce.apache.org%3EMailing List
https://lists.apache.org/thread.html/rb5b0e46f179f60b0c70204656bc52fcb558e961cb4d06a971e9e3efb%40%3Cusers.httpd.apache.org%3EMailing List
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RMIIEFINL6FUIOPD2A3M5XC6DH45Y3CC/Release Notes
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WS5RVHOIIRECG65ZBTZY7IEJVWQSQPG3/Release Notes
https://security.gentoo.org/glsa/202208-20Third Party Advisory
https://security.netapp.com/advisory/ntap-20211029-0009/Third Party Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-pathtrv-LAzg68cZThird Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.htmlPatch, Third Party Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-41773US Government Resource

Timeline

Published: Oct 5, 2021
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2021-41773?

How severe is CVE-2021-41773?

CVE-2021-41773 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 99.99% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.

How do I fix CVE-2021-41773?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-41773?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST