From pub 3920. Link. https://www.irs.gov/publications/p3920#en_US_201409_publink10005705

Disability Payments

For tax years ending after September 10, 2001, disability payments (including Social Security Disability Insurance (SSDI) payments) are not included in income if they are for injuries incurred as a direct result of a terrorist attack (including the September 11 attacks, anthrax attacks, and Oklahoma City attack) directed against the United States (or its allies). However, you must include in your income any disability payments you received or you would have received in retirement had you not become disabled as a result of a terrorist attack.