CVE-2026-54513

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.

## Summary `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. ## Impact Applications using `BasicPolymorphicTypeValidator` with `allowIfSubTypeIsArray()` as a safeguard get no protection for concrete array component types; an attacker controlling JSON can instantiate non-allowlisted types via an array wrapper, re-opening the gadget-instantiation risk PTV is meant to prevent. ## Affected / Patched (verified via `git tag --contains`) - 2.18 line: `>= 2.10.0, < 2.18.8` -> fixed in **2.18.8** - 2.19-2.21 line: `>= 2.19.0, < 2.21.4` -> fixed in **2.21.4** - 3.x line: `>= 3.0.0, < 3.1.4` -> fixed in **3.1.4** `PolymorphicTypeValidator` was added in 2.10.0 so vulnerability N/A for versions prior to that. ## Severity / CWE Maintainer: significant. Reporter: HIGH. CWE-184 (Incomplete List of Disallowed Inputs); related CWE-502. ## Upstream fix FasterXML/jackson-databind#5981; fix PR #5983 (`24529da`), 2.18 backport PR #5984 (`01d1692`). Released 2026-06-04 in 2.18.8 / 2.21.4 / 3.1.4. ## Credits Omkhar Arasaratnam (@omkhar) - finder.

## Summary `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. ## Impact Applications using `BasicPolymorphicTypeValidator` with `allowIfSubTypeIsArray()` as a safeguard get no protection for concrete array component types; an attacker controlling JSON can instantiate non-allowlisted types via an array wrapper, re-opening the gadget-instantiation risk PTV is meant to prevent. ## Affected / Patched (verified via `git tag --contains`) - 2.18 line: `>= 2.10.0, < 2.18.8` -> fixed in **2.18.8** - 2.19-2.21 line: `>= 2.19.0, < 2.21.4` -> fixed in **2.21.4** - 3.x line: `>= 3.0.0, < 3.1.4` -> fixed in **3.1.4** `PolymorphicTypeValidator` was added in 2.10.0 so vulnerability N/A for versions prior to that. ## Severity / CWE Maintainer: significant. Reporter: HIGH. CWE-184 (Incomplete List of Disallowed Inputs); related CWE-502. ## Upstream fix FasterXML/jackson-databind#5981; fix PR #5983 (`24529da`), 2.18 backport PR #5984 (`01d1692`). Released 2026-06-04 in 2.18.8 / 2.21.4 / 3.1.4. ## Credits Omkhar Arasaratnam (@omkhar) - finder.

jackson-databind contiene la funcionalidad de enlace de datos de propósito general y el modelo de árbol para Jackson Data Processor. Desde 2.10.0 hasta 2.18.8, 2.21.4 y 3.1.4, BasicPolymorphicTypeValidator.Builder.allowIfSubTypeIsArray() permite cualquier tipo de array basándose únicamente en clazz.isArray(), sin validar el tipo de componente (elemento) del array contra la lista de permitidos configurada. Un PTV construido con allowIfSubTypeIsArray() más una lista de permitidos explícita de tipo concreto, por lo tanto, todavía permite EvilType[] aunque EvilType no esté en la lista de permitidos. Cuando Jackson deserializa los elementos y no hay IDs de tipo por elemento presentes, instancia el tipo de componente directamente sin una verificación PTV adicional, eludiendo la lista de permitidos. Esta vulnerabilidad está corregida en 2.18.8, 2.21.4 y 3.1.4.