CVE-2021-41773

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.

Gravité et risque d'exploitation

CVE-2021-41773 obtient un score CVSS de 7.5/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 99.99 %, ce qui la place devant 100.0 % des CVE référencées.

Que faire ?

• Vérifiez si Apache HTTP Server (versions Apache HTTP Server 2.4 2.4.49) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://httpd.apache.org/security/vulnerabilities_24.html
• https://lists.apache.org/thread.html/r6abf5f2ba6f1aa8b1030f95367aaf17660c4e4c78cb2338aee18982f%40%3Cusers.httpd.apache.org%3E
• https://lists.apache.org/thread.html/r98d704ed4377ed889d40479db79ed1ee2f43b2ebdd79ce84b042df45%40%3Cannounce.apache.org%3E
• 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.apache.org%3E
• https://lists.apache.org/thread.html/rb5b0e46f179f60b0c70204656bc52fcb558e961cb4d06a971e9e3efb%40%3Cusers.httpd.apache.org%3E
• http://www.openwall.com/lists/oss-security/2021/10/07/6
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-pathtrv-LAzg68cZ
• http://www.openwall.com/lists/oss-security/2021/10/08/1
• https://lists.apache.org/thread.html/r17a4c6ce9aff662efd9459e9d1850ab4a611cb23392fc68264c72cb3%40%3Ccvs.httpd.apache.org%3E
• 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.html
• http://www.openwall.com/lists/oss-security/2021/10/11/4
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RMIIEFINL6FUIOPD2A3M5XC6DH45Y3CC/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WS5RVHOIIRECG65ZBTZY7IEJVWQSQPG3/
• http://www.openwall.com/lists/oss-security/2021/10/15/3
• http://www.openwall.com/lists/oss-security/2021/10/16/1
• https://www.oracle.com/security-alerts/cpujan2022.html
• https://security.netapp.com/advisory/ntap-20211029-0009/
• http://packetstormsecurity.com/files/164629/Apache-2.4.49-2.4.50-Traversal-Remote-Code-Execution.html
• http://packetstormsecurity.com/files/164941/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.html
• https://security.gentoo.org/glsa/202208-20