CVE-2020-26032 in Zammad
Summary
by MITRE • 12/28/2020
An SSRF issue was discovered in Zammad before 3.4.1. The SMS configuration interface for Massenversand is implemented in a way that renders the result of a test request to the User. An attacker can use this to request any URL via a GET request from the network interface of the server. This may lead to disclosure of information from intranet systems.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 12/28/2020
The identified vulnerability represents a server-side request forgery flaw in Zammad versions prior to 3.4.1 that specifically affects the Massenversand SMS configuration interface. This security weakness stems from inadequate input validation and sanitization within the test request functionality, allowing malicious actors to manipulate the system into making unauthorized network requests on behalf of the server. The vulnerability resides in the way the application handles user-provided URLs during SMS configuration testing, creating an attack vector that bypasses normal network access controls.
The technical implementation of this flaw enables attackers to leverage the server's network interface directly through a simple GET request mechanism. When users attempt to test SMS configurations, the system performs background requests to validate connectivity or retrieve information from specified endpoints. However, the validation process fails to properly restrict or sanitize the target URLs, allowing arbitrary external addresses to be accessed. This creates a pathway where an attacker can probe internal network resources that would normally be protected by firewalls or other network segmentation controls.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with potential access to sensitive internal systems and services. The server may inadvertently expose internal network endpoints, database connections, or administrative interfaces that are typically isolated from external access. This reconnaissance capability can enable further exploitation attempts, including the discovery of additional vulnerabilities within the internal network infrastructure. The attack surface increases significantly when considering that the vulnerable interface may be accessible to authenticated users with limited privileges, potentially enabling privilege escalation scenarios.
This vulnerability aligns with CWE-918, which specifically addresses server-side request forgery conditions where applications fail to properly validate and sanitize external resource requests. The flaw also maps to ATT&CK technique T1046, which covers network service scanning, as attackers can use this vulnerability to map internal network topology and identify accessible services. Additionally, the issue demonstrates characteristics of T1566, representing a credential access vector through information disclosure attacks that can reveal internal system configurations and potentially lead to further compromise.
Organizations should implement immediate mitigations including input validation for all URL parameters within the SMS configuration interface, implementing strict allowlists for permitted external endpoints, and restricting network access from the Zammad server to internal systems through firewall rules. The most effective long-term solution involves upgrading to Zammad version 3.4.1 or later where the vulnerability has been patched. Network segmentation should be enforced to limit what internal resources the application can access, while implementing proper logging and monitoring of external requests to detect anomalous behavior patterns that may indicate exploitation attempts.