CVE-2026-67216: cJSON cJSON_Compare Exponential Complexity Denial of Service

cJSON through 1.7.19 contains an inefficient algorithmic complexity flaw in cJSONCompare(). When comparing objects, the function recurses into each shared subtree twice, once in each direction, with no depth guard, making the running time exponential in nesting depth. A small, deeply nested document of a few hundred bytes (depth around 40) compared for equality consumes hours of CPU, and the cost roughly doubles with each additional level of nesting. An application that calls cJSONCompare() on attacker-influenced JSON that is structurally equal to a reference document is exposed to a denial-of-service condition.