Medium · published July 29, 2026
nanoid (Nano ID) before 3.3.16 and 5.1.16 contains an infinite loop in the customAlphabet and nanoid functions of its non-secure module (nanoid/non-secure). When these functions are given a negative size, the loop counter is decremented from a negative value and never reaches its termination condition, spinning indefinitely and hanging the calling thread. An application that passes an unvalidated, attacker-controlled negative size to these functions is exposed to a denial-of-service condition.
| Product | Versions | Fixed in |
|---|---|---|
| nanoid_project/nanoid | < 3.3.16 | 3.3.16 |
| nanoid_project/nanoid | ≥ 4.0.0, < 5.1.16 | 5.1.16 |