High · published June 24, 2026
jackson-databind contains the general-purpose data-binding functionality and tree-model for Jackson Data Processor. From 2.10.0 until 2.18.8, 2.21.4, and 3.1.4, BasicPolymorphicTypeValidator.Builder.allowIfSubTypeIsArray() allowlists any array type based only on clazz.isArray(), without validating the array's component (element) type against the configured allowlist. A PTV built with allowIfSubTypeIsArray() plus an explicit concrete-type allowlist therefore still permits EvilType[] even though EvilType is not allowlisted. When Jackson deserializes the elements and no per-element type IDs are present, it instantiates the component type directly with no further PTV check, bypassing the allowlist. This vulnerability is fixed in 2.18.8, 2.21.4, and 3.1.4.
| Product | Versions | Fixed in |
|---|---|---|
| fasterxml/jackson-databind | ≥ 2.10.0, < 2.18.8 | 2.18.8 |
| fasterxml/jackson-databind | ≥ 2.19.0, < 2.21.4 | 2.21.4 |
| fasterxml/jackson-databind | ≥ 3.0.0, < 3.1.4 | 3.1.4 |