Jackson Databind

jackson-databind validates the outer class of a class-name type ID but accepts attacker-selected classes inside its generic arguments, even when those classes violate the declared type or would be rejected as direct type IDs. This bypasses the generic-argument validation added for CVE-2026-54512 (GHSA-j3rv-43j4-c7qm), of which this is an incomplete fix. DatabindContext._resolveAndValidateGeneric() checks the outer class against the declared base type and then passes each argument from the type ID to _validateTypeParameter(), which validates the argument against the outer base type rather than enforcing its corresponding declared generic binding. It also invokes validators with arguments that have not passed the subtype check those validators expect. Under the default DefaultBaseTypeLimitingValidator this accepts an unrelated class inside a generic subtype even when the same class is rejected as a direct type ID. Where an allowIfBaseType(...) rule approves the outer type, Jackson substitutes LaissezFaireSubTypeValidator, so the configured validator no longer restricts the embedded arguments. The element type of a plain array type ID such as [Lpkg.Gadget; is likewise left unvalidated once the array's base type is approved. Affected paths include annotation-based class-name polymorphism with a default Jackson 3.x JsonMapper, configured default typing in both Jackson 2.x and 3.x, and integrations that expose that default typing. The default-validator case requires no application-authored validator: with @JsonTypeInfo(use = Id.CLASS), a direct gadget type ID is rejected as "Not a subtype", while a type ID naming a generic wrapper around the same gadget is accepted and deserialized, including attacker-supplied bean properties. Where class-name default typing permits Map, a property declared as Map<String,String> accepts HashMap<FileSystemXmlApplicationContext,String>; map-key discovery then passes the attacker-controlled JSON property name to the selected class's one-string constructor. With Spring on the classpath and attacker-controlled XML the application can load, that constructor loads the XML and invokes ProcessBuilder.start() under the application account, giving arbitrary command execution. This issue affects com.fasterxml.jackson.core:jackson-databind from 2.10.0 and tools.jackson.core:jackson-databind from 3.0.0. Releases before 2.10.0 are not affected, because PolymorphicTypeValidator was introduced in jackson-databind 2.10.0.

Published: 2026-10-28T00:07:41.577Z
Updated: 2026-10-28T00:07:41.577Z

TypeDeserializerBase._findDeserializer() in FasterXML jackson-databind caches the resolved deserializer under the raw, attacker-supplied type ID. When name-based polymorphism is configured with a fallback, for example @JsonTypeInfo(use = Id.NAME, defaultImpl = ...), every distinct unrecognized type ID resolves to the same fallback deserializer but is retained as its own key in the _deserializers map. That map has no configurable bound and lives for the lifetime of the type deserializer, so an attacker who can repeatedly supply fresh unknown type IDs causes monotonic memory retention across requests. The reporter observed 10,000 retained entries from 10,000 distinct unknown IDs, against a single entry for a control that repeated one unknown ID the same number of times, isolating attacker-controlled key cardinality from request volume. Exploitation requires an application that enables name-based polymorphism with a defaultImpl or equivalent fallback, accepts attacker-influenced type IDs, and reuses a long-lived ObjectMapper across requests. The fix stops caching fallback resolutions for unrecognized IDs and bounds both the number of cached entries and the length of a cacheable type ID.

Published: 2026-09-23T02:17:50.480Z
Updated: 2026-09-23T14:03:16.129Z

Forward-reference completion for @JsonIdentityInfo object IDs in FasterXML jackson-databind performs a linear scan of the pending-reference accumulator for every resolved ID. The affected paths are CollectionDeserializer.CollectionReferringAccumulator.resolveForwardReference() and the equivalent implementation in MapDeserializer. When a document first creates N unresolved object-ID references in an identity-enabled collection or map and then defines those same IDs in reverse order, completion performs on the order of N * (N + 1) / 2 identity comparisons, so a shallow document whose size grows linearly causes quadratic CPU work during deserialization. The reporter instrumented equals() calls on the ID class and measured exactly 2,003,000 comparisons at N = 2,000, against zero comparisons in the pending-reference lookup path for an equally sized control in which every reference was already resolved. The input requires no deep nesting and no syntactically unusual JSON. Exploitation requires an application that deserializes attacker-influenced JSON into an identity-enabled collection or map. The fix replaces the repeated linear lookup with a keyed pending-reference structure.

Published: 2026-09-23T02:21:48.323Z
Updated: 2026-09-23T14:05:17.919Z

jackson-databind binds a JSON string to a javax.xml.datatype.Duration or javax.xml.datatype.XMLGregorianCalendar field by passing the raw string verbatim to DatatypeFactory.newDuration(value) or newXMLGregorianCalendar(value) in CoreXMLDeserializers.Std._deserialize. These deserializers are registered by default with no opt-in, so a plain ObjectMapper or JsonMapper with no polymorphic typing and no special configuration reaches this path. The XML Schema lexical grammar permits numeric components of arbitrary length, which the JDK materializes through the native BigInteger(String) and BigDecimal(String) constructors, both quadratic in digit count. Because the digits sit inside a JSON string token rather than a JSON number token, jackson-core's StreamReadConstraints.maxNumberLength guard never applies; jackson's own NumberDeserializers call validateIntegerLength or validateFPLength before parsing a stringified number, but the XML datatype deserializer omits that pre-check. An unauthenticated attacker can therefore submit a single request of a few megabytes, such as a Duration value consisting of the letter P followed by several million digits and the letter Y, and force tens of seconds to several minutes of single-threaded CPU work; a handful of concurrent requests can saturate a server's worker threads. This affects com.fasterxml.jackson.core:jackson-databind from 2.0.0 before 2.18.10, from 2.19.0 before 2.21.6, and from 2.22.0 before 2.22.2, and tools.jackson.core:jackson-databind from 3.0.0 before 3.1.6 and from 3.2.0 before 3.2.2. Users should upgrade to 2.18.10, 2.21.6, 2.22.2, 3.1.6, or 3.2.2.

Published: 2026-09-11T15:49:30.366Z
Updated: 2026-09-11T16:32:46.146Z

jackson-databind contains the general-purpose data-binding functionality and tree-model for Jackson Data Processor. From 2.18.0 until 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1, UnwrappedPropertyHandler.processUnwrapped() replays buffered JSON for a @JsonUnwrapped property and calls prop.deserializeAndSet() without a prop.visibleInView(ctxt.getActiveView()) guard, allowing a property annotated with both @JsonView and @JsonUnwrapped to be written from attacker JSON under a less-privileged active view. This issue is fixed in versions 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1.

Published: 2026-07-14T19:57:48.473Z
Updated: 2026-10-19T19:32:26.642Z