Race condition in the WorkerPrivate::NotifyFeatures function in Mozilla Firefox before 41.0 allows remote attackers to execute arbitrary code or cause a denial of service (use-after-free and application crash) by leveraging improper interaction between shared workers and the IndexedDB implementation.
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.