CVE-2020-10101 in Zammad
Summary
by MITRE
An issue was discovered in Zammad 3.0 through 3.2. The WebSocket server crashes when messages in non-JSON format are sent by an attacker. The message format is not properly checked and parsing errors not handled. This leads to a crash of the service process.
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Analysis
by VulDB Data Team • 04/09/2024
The vulnerability identified as CVE-2020-10101 affects Zammad versions 3.0 through 3.2, specifically targeting the WebSocket server implementation within the application. This issue represents a classic input validation and error handling weakness that can be exploited to cause a denial of service condition. The WebSocket protocol serves as a critical communication channel for real-time updates and interactive features within Zammad's web interface, making this vulnerability particularly concerning for organizations relying on the platform for customer service management and ticketing operations. The flaw exists in the server-side message processing logic where incoming WebSocket messages undergo insufficient validation before being parsed.
The technical root cause of this vulnerability stems from inadequate message format validation and improper error handling mechanisms within the WebSocket server component. When an attacker sends a malformed message that does not conform to the expected JSON format, the server fails to gracefully handle the parsing error. Instead of implementing proper exception handling or fallback mechanisms, the system crashes entirely upon encountering non-JSON content. This behavior aligns with CWE-248, which addresses "Uncaught Exception" conditions in software applications. The lack of defensive programming practices means that any malformed input can trigger an unhandled exception that propagates up through the application stack, ultimately causing the service process to terminate and resulting in a complete service disruption.
The operational impact of this vulnerability extends beyond simple service interruption, as it creates a potential attack vector for malicious actors seeking to disrupt Zammad operations. Attackers can exploit this weakness by establishing a WebSocket connection to the target system and sending carefully crafted non-JSON messages to induce the server crash. This type of denial of service attack can be executed with minimal resources and technical expertise, making it particularly dangerous in production environments where continuous availability is critical. Organizations using Zammad for customer support operations may experience significant downtime, potentially affecting their ability to respond to customer inquiries and manage support tickets effectively. The vulnerability also exposes the system to potential reconnaissance activities, as attackers can use this weakness to identify the presence of Zammad installations and assess their version information.
Mitigation strategies for CVE-2020-10101 should focus on implementing robust input validation and error handling mechanisms within the WebSocket server. Organizations should upgrade to patched versions of Zammad where the vulnerability has been addressed through proper message format validation and exception handling. The fix should include comprehensive JSON parsing validation with appropriate error recovery mechanisms that prevent crashes when malformed input is received. Additionally, implementing rate limiting and connection monitoring can help detect and mitigate potential abuse of this vulnerability. Security practitioners should also consider deploying network-level protections such as firewalls or intrusion detection systems that can monitor for suspicious WebSocket traffic patterns. The remediation process should align with ATT&CK technique T1499.004, which addresses "Endpoint Denial of Service" by ensuring proper handling of malformed inputs and implementing robust error recovery mechanisms to prevent service disruption. Organizations should also conduct thorough testing of their WebSocket implementations to verify that all input paths properly handle unexpected formats without causing system crashes or service interruptions.