Envoy Normalized HTTP URL Paths Access Control Bypass Vulnerability [CVE-2019-9901]

CVE Number – CVE-2019-9901

A vulnerability in Envoy could allow an unauthenticated, remote attacker to bypass security restrictions and conduct directory traversal attacks.The vulnerability exists because the affected software fails to normalize HTTP URL paths. An attacker could exploit this vulnerability by submitting a crafted URL to the targeted system. A successful exploit could allow the attacker to bypass access controls and conduct directory traversal attacks on the targeted system.Envoy Proxy has confirmed the vulnerability and released software updates.


  • To exploit this vulnerability, an attacker must send a crafted URL to be processed by the targeted system. This access requirement may reduce the likelihood of a successful exploit.


  • Administrators are advised to apply the appropriate updates.Administrators are advised to allow only trusted users to have network access.Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.Administrators can help protect affected systems from external attacks by using a solid firewall strategy.Administrators are advised to monitor affected systems.

Vendor Announcements

  • Envoy Proxy has released an issue report at the following link: CVE-2019-9901

Fixed Software

  • Envoy Proxy has released software updates at the following link: Envoy releases

Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: