Arbitrary code execution via PolymorphicTypeValidator bypass

Summary

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. A flaw was found in jackson-databind. This vulnerability allows a remote attacker to bypass the PolymorphicTypeValidator (PTV) when polymorphic typing is enabled and a type identifier contains generic parameters. By crafting a malicious type ID, an attacker can place a denied class as a generic type parameter of an allowed container. This leads to the loading and instantiation of arbitrary classes, potentially resulting in arbitrary code execution. This vulnerability in `jackson-databind` is rated as Important. While it describes a potential bypass of the PolymorphicTypeValidator leading to arbitrary code execution, exploitation requires an attacker to already possess administrative privileges, specifically the `manage-realm` role. This flaw does not enable privilege escalation, as it does not grant additional capabilities beyond those inherently available to an existing administrator. Red Hat severity: Important — CVSS 8.1 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-502. No fixing RHSA erratum has published yet; monitor the Red Hat CVE page and patch when it ships. Will not fix / out of support: Red Hat build of Debezium 3.