I am sorry to hear about this. First, you need to check your contract to see if it has an provision relating to your employer's right to terminate the agreement early. Anything about employment "at will," or employment subject to the underlying project moving forward would be the sorts of things you are looking for.
Assuming that no such clause exists and there was a guarantee of employment until December, it is likely that you would have a claim for breach of contract if they don't supply you with alternative work. You would have a duty to "mitigate your damages," meaning a duty to try and find another job as soon as possible to minimize the loss of income you will suffer from this breach of contract, but an individual in your circumstance should be able to collect damages in the amount of the income you lose before you find a replacement job. If the replacement job pays less, you would also be entitled to the difference up to December.
The first step is usually a demand letter, threatening legal action unless you are either brought back on for a different project or compensated for the income you will lose as a result of the early termination and breach of contract.
I hope that you find this information helpful. Please do not hesitate to let me know if you have any questions or concerns regarding the above and I will be more than happy to assist you further.
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