Nezha Monitoring is a self-hostable, lightweight, servers and websites monitoring and O&M tool. From 2.2.7 until 2.2.11, ServiceSentinel.worker in service/singleton/servicesentinel.go checked an owned service under servicesLock and later dereferenced pointer-valued serviceStatusToday and serviceCurrentStatusData entries under serviceResponseDataStoreLock without revalidating that ServiceSentinel.Delete had not removed them. A RoleMember could concurrently report TCP or ICMP results through the members own agent and delete the same owned service, causing a nil pointer dereference. Because the gRPC server had no recovery interceptor, the worker panic terminated the whole dashboard process and disrupted every tenants web interface, REST API, and agent connections. The issue affects availability only and does not disclose or modify data. This issue is fixed in versions 2.2.11 and 2.3.0.
Weakness
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Extended Description
A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:
A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.
Potential Mitigations
- Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
- Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).