jackson-databind: PolymorphicTypeValidator bypass via generic type arguments and array element types allows arbitrary class instantiation (incomplete fix for CVE-2026-54512)

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-110879
StatePUBLISHED
AssignerHeroDevs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-28 01:16:55 UTC
Updated2026-10-28 15:21:31 UTC
Descriptionjackson-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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from 36c7be3b-2937-45df-85ea-ca7133ea542c

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.011960000 probability, percentile 0.679760000 (date 2026-10-28)

Problem Types: CWE-502 | CWE-502 CWE-502 Deserialization of Untrusted Data

VersionSourceTypeScoreSeverityVector
3.136c7be3b-2937-45df-85ea-ca7133ea542cSecondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNACVSS9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA FasterXML Jackson-databind affected 2.10.0 2.18.12 maven Not specified
CNA FasterXML Jackson-databind unaffected 2.18.12 maven Not specified
CNA FasterXML Jackson-databind affected 2.19.0 2.21.8 maven Not specified
CNA FasterXML Jackson-databind unaffected 2.21.8 maven Not specified
CNA FasterXML Jackson-databind affected 2.22.0 2.22.4 maven Not specified
CNA FasterXML Jackson-databind unaffected 2.22.4 maven Not specified
CNA FasterXML Jackson-databind affected 3.0.0 3.1.8 maven Not specified
CNA FasterXML Jackson-databind unaffected 3.1.8 maven Not specified
CNA FasterXML Jackson-databind affected 3.2.0 3.2.4 maven Not specified
CNA FasterXML Jackson-databind unaffected 3.2.4 maven Not specified

References

ReferenceSourceLinkTags
www.cve.org/CVERecord 36c7be3b-2937-45df-85ea-ca7133ea542c www.cve.org
github.com/FasterXML/jackson-databind/security/advisories/GHSA-m8xf-2cr7... 36c7be3b-2937-45df-85ea-ca7133ea542c github.com
github.com/FasterXML/jackson-databind/security/advisories/GHSA-j3rv-43j4... 36c7be3b-2937-45df-85ea-ca7133ea542c github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: martinfrancois (en)

CNA: AdamKorcz (en)

CNA: cowtowncoder (Tatu Saloranta) (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-10-20T22:44:00.000ZGHSA-m8xf-2cr7-77ph published by the maintainer in FasterXML/jackson-databind

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