Junglewise Threat Intelligence

CVE-2026-54513: FasterXML jackson-databind validation bypass in BasicPolymorphicTypeValidator

CVE-2026-54513 · Severity: high · CVSS 8.1 · Published 2026-06-23

Technologies: FasterXML Jackson Databind. Vendors: FasterXML.

Executive brief

FasterXML jackson-databind is a popular Java library used for converting data between Java objects and formats like JSON. A security flaw in its validation mechanism allows an attacker to bypass security allowlists by using array types. This could lead to the execution of unauthorized code or other malicious actions when the application processes specially crafted data.

Technical details

A vulnerability exists in jackson-databind's BasicPolymorphicTypeValidator (PTV) where the allowIfSubTypeIsArray() method fails to validate the component type of an array against the configured allowlist. While the validator correctly checks if a class is an array, it does not perform a secondary check on the element type during deserialization if per-element type IDs are missing. This allows an attacker to bypass PTV restrictions by wrapping a forbidden 'EvilType' in an array (e.g., EvilType[]), leading to the instantiation of unauthorized classes. The issue is fixed in versions 2.18.8, 2.21.4, and 3.1.4.

Affected products

  • FasterXML jackson-databind >= 2.10.0, < 2.18.8; >= 2.19.0, < 2.21.4; >= 3.0.0, < 3.1.4

Timeline

  • 2026-05-08: patched: Fixes committed to 2.18 and 3.x branches
  • 2026-06-23: disclosed: CVE published to NVD

References

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