Helping Apache Servers stay safe from zero-day path traversal attacks (CVE-2021-41773)


On September 29, 2021, the Apache Security team was alerted to a path traversal vulnerability being actively exploited (zero-day) against Apache HTTP Server version 2.4.49. The vulnerability, in some instances, can allow an attacker to fully compromise the web server via remote code execution (RCE) or at the very least access sensitive files. CVE number 2021-41773 has been assigned to this issue. Both Linux and Windows based servers are vulnerable.
An initial patch was made available on October 4 with an update to 2.4.50, however, this was found to be insufficient resulting in an additional patch bumping the version number to 2.4.51 on October 7th (CVE-2021-42013).
Customers using Apache HTTP Server versions 2.4.49 and 2.4.50 should immediately update to version 2.4.51 to mitigate the vulnerability. Details on how to update can be found on the official Apache HTTP Server project site.
Any Cloudflare customer with the setting normalize URLs to origin turned on have always been protected against this vulnerability.
Additionally, customers who have access to the Cloudflare Web Application Firewall (WAF), receive additional protection by turning on the rule with the following IDs:
1c3d3022129c48e9bb52e953fe8ceb2f(for Continue reading





