CVE-2020-26029: 
NixOS vulnerability analysis and mitigation

An authorization vulnerability (CVE-2020-26029) was discovered in Zammad versions before 3.4.1. The issue involves incorrect authorization checks for impersonation requests that are made via the X-On-Behalf-Of header. The vulnerability was disclosed on September 22, 2020, and affects Zammad versions 1.0.x up to 3.4.0 (Zammad Advisory, NVD).

The vulnerability stems from a flaw in how Zammad handles authorization checks for impersonation requests. When processing requests with the X-On-Behalf-Of header, the system performs authorization checks against the actual user making the request instead of the user specified in the X-On-Behalf-Of header. This implementation error could allow attackers to bypass proper authentication checks and gain unauthorized access to information (Zammad Advisory).

The vulnerability allows attackers to potentially gain unauthorized access to information by exploiting the improper authorization checks. Since the system validates permissions against the wrong user context, an attacker could perform actions with elevated privileges that they shouldn't have access to (Zammad Advisory).

The vulnerability requires an attacker to have access to make requests with the X-On-Behalf-Of header to the Zammad system. The issue is exploitable by manipulating impersonation requests to bypass intended authorization restrictions (Zammad Advisory).

The vulnerability has been fixed in Zammad version 3.4.1 and 3.5.0. Users are recommended to upgrade to one of these fixed versions. The updates are available through the official Zammad website, FTP server, or through OS package managers (Zammad Advisory).