CVE-2026-54512: jackson-databind: PolymorphicTypeValidator bypass via generic type parameters allows arbitrary class instantiation

Vulnerability summary

CVE-2026-54512 is a high (CVSS 8.1) Incomplete List of Disallowed Inputs vulnerability in fasterxml jackson-databind. EPSS estimates a 1.07% chance of exploitation in the next 30 days, higher than 64.8% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 23-06-2026
   PublishedVulnerability first disclosed.
2. 24-06-2026
   Last modifiedVulnerability information updated.

Description

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, jackson-databind's PolymorphicTypeValidator (PTV) is the primary safety mechanism guarding polymorphic deserialization. When polymorphic typing is enabled and a type identifier contains generic parameters (i.e. the type ID string contains <), DatabindContext._resolveAndValidateGeneric() validates only the raw container class name (the substring before <) against the configured PTV. If the container type is approved, the method parses the full canonical type string via TypeFactory.constructFromCanonical() and returns the fully parameterized type without ever validating the nested type arguments against the PTV. The nested type arguments are then resolved, instantiated, and populated as beans during deserialization. An attacker who controls the type ID can therefore place a denied class as a generic type parameter of an allowed container — for example java.util.ArrayList<com.evil.Gadget> when only java.util.ArrayList is allow-listed. The container passes the PTV check; com.evil.Gadget is loaded via Class.forName(name, true, loader), instantiated, and its properties are set from attacker-controlled JSON. This completely bypasses an explicitly configured PTV allow-list. This vulnerability is fixed in 2.18.8, 2.21.4, and 3.1.4.

• CWE-184Incomplete List of Disallowed InputsThe product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete.
• CWE-502Deserialization of Untrusted DataThe product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.