CVE-2020-26033 in Zammad
Summary
by MITRE • 12/28/2020
An issue was discovered in Zammad before 3.4.1. The Tag and Link REST API endpoints (for add and delete) lack a CSRF token check.
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Analysis
by VulDB Data Team • 12/28/2020
The vulnerability identified in Zammad versions prior to 3.4.1 represents a critical security flaw in the application's REST API implementation that directly impacts the integrity of tag and link management functionalities. This issue stems from the absence of Cross-Site Request Forgery protection mechanisms within the Tag and Link REST API endpoints specifically designed for add and delete operations. The vulnerability exposes the system to unauthorized modifications that could potentially compromise data integrity and system availability.
The technical nature of this flaw can be categorized under CWE-352, which specifically addresses Cross-Site Request Forgery vulnerabilities. This weakness allows attackers to perform unauthorized actions on behalf of legitimate users by exploiting the trust relationship between the web application and its users. The absence of CSRF token validation in these particular API endpoints creates a pathway for malicious actors to craft crafted requests that could manipulate tag and link data without proper authorization. The vulnerability exists at the application layer where authentication and authorization controls should be enforced, but instead relies on implicit trust mechanisms that can be easily bypassed.
From an operational impact perspective, this vulnerability presents significant risks to system security and data integrity. Attackers who can identify valid API endpoints could potentially inject malicious tags or links into the system, manipulate existing tag associations, or delete critical link relationships. This could lead to data corruption, information leakage, or disruption of service availability. The attack surface is particularly concerning because REST APIs are often designed to be accessible programmatically, making them attractive targets for automated exploitation. The vulnerability also aligns with ATT&CK technique T1566 which covers phishing with a malicious attachment, as attackers could potentially embed malicious API calls within crafted payloads that appear legitimate to users.
The exploitation of this vulnerability typically requires an attacker to have knowledge of the specific API endpoints and their expected parameters, along with the ability to craft requests that can bypass authentication mechanisms. This flaw particularly affects organizations that rely heavily on tagging and linking features for content management, ticket tracking, or organizational data structures. The impact extends beyond simple data modification as it could potentially enable more sophisticated attacks such as privilege escalation or data exfiltration through manipulated tag relationships that might be used for access control purposes.
Organizations should implement immediate mitigations including the enforcement of CSRF tokens for all state-changing REST API operations, particularly those related to data modification functions. The recommended approach involves implementing proper token validation mechanisms that generate unique tokens for each user session and validate them against requests before processing any tag or link modifications. Additionally, organizations should conduct comprehensive security assessments of their API implementations to identify other endpoints that may be similarly vulnerable. The upgrade to Zammad version 3.4.1 or later represents the primary remediation strategy as this release includes proper CSRF protection mechanisms that address the identified weakness in the authentication and authorization controls for REST API operations.
The broader implications of this vulnerability highlight the importance of implementing consistent security controls across all application interfaces, particularly when dealing with state-changing operations. Organizations should establish comprehensive API security policies that mandate CSRF protection for all REST endpoints that modify system data or user permissions. This incident underscores the need for continuous security testing and validation of authentication mechanisms, as well as adherence to established security frameworks such as OWASP API Security Top 10 which emphasizes the importance of protecting against unauthorized operations through proper request validation and token management. The vulnerability serves as a reminder that even seemingly simple operations like tagging or linking require robust security controls when exposed through programmatic interfaces.