jackson-databind omits java.lang.Comparable from DefaultBaseTypeLimitingValidator's unsafe base types

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-83557
StatePUBLISHED
AssignerHeroDevs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-01 15:17:37 UTC
Updated2026-09-01 18:17:47 UTC
DescriptionDefaultBaseTypeLimitingValidator is the PolymorphicTypeValidator applied automatically whenever @JsonTypeInfo is used without an explicitly configured custom validator. It denies polymorphic resolution only for a fixed set of "unsafe base types", and its isSafeSubType method returns true unconditionally for every base type outside that set. java.lang.Comparable was absent from the list despite being implemented by a very large fraction of JDK and application classes, comparable in breadth to java.io.Serializable, which is on the list for that reason. An application declaring an @JsonTypeInfo-annotated property or class with Comparable as its base type, and no custom PolymorphicTypeValidator, will accept a type identifier for essentially any class implementing Comparable. This yields an attacker-controlled object instantiation primitive; a demonstrated case constructs a java.io.File for an arbitrary attacker-chosen path, which becomes path-traversal-adjacent if the application subsequently calls path-sensitive methods on the value. No class implementing Comparable has been identified that yields code execution through deserialization alone. Global Default Typing via activateDefaultTyping is not affected, because that method structurally requires an explicit PolymorphicTypeValidator argument. This affects com.fasterxml.jackson.core:jackson-databind from 2.11.0 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.

Risk And Classification

Primary CVSS: v3.1 5.6 MEDIUM from 36c7be3b-2937-45df-85ea-ca7133ea542c

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

EPSS: 0.005860000 probability, percentile 0.457610000 (date 2026-09-02)

Problem Types: CWE-502 | CWE-915 | CWE-502 CWE-502 Deserialization of Untrusted Data | CWE-915 CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes

VersionSourceTypeScoreSeverityVector
3.136c7be3b-2937-45df-85ea-ca7133ea542cSecondary5.6MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
3.1CNACVSS5.6MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA FasterXML Jackson-databind affected 2.11.0 2.18.10 maven Not specified
CNA FasterXML Jackson-databind affected 2.19.0 2.21.6 maven Not specified
CNA FasterXML Jackson-databind affected 2.22.0 2.22.2 maven Not specified
CNA FasterXML Jackson-databind affected 3.0.0 3.1.6 maven Not specified
CNA FasterXML Jackson-databind affected 3.2.0 3.2.2 maven Not specified

References

ReferenceSourceLinkTags
github.com/FasterXML/jackson-databind/security/advisories/GHSA-gx83-3vf8... 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/FasterXML/jackson-databind/commit/eb3b7fc0f9c0d27f471550ac331... 36c7be3b-2937-45df-85ea-ca7133ea542c github.com
github.com/FasterXML/jackson-databind/pull/6155 36c7be3b-2937-45df-85ea-ca7133ea542c github.com
github.com/FasterXML/jackson-databind/issues/6156 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: prvazsahnazarov (en)

CNA: Tatu Saloranta (cowtowncoder) (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-08-11T02:58:00.000ZFix committed upstream (FasterXML/jackson-databind#6155)
CNA2026-09-01T00:00:00.000ZGitHub Security Advisory GHSA-gx83-3vf8-gh7j published by the maintainer

Solutions

CNA: Upgrade to jackson-databind 2.18.10, 2.21.6, 2.22.2 (com.fasterxml.jackson.core) or 3.1.6, 3.2.2 (tools.jackson.core). The fix adds java.lang.Comparable to the UnsafeBaseTypes denylist in DefaultBaseTypeLimitingValidator, so polymorphic resolution against a Comparable base type is denied outright. Applications that legitimately need polymorphic handling of a Comparable-typed property must configure an explicit PolymorphicTypeValidator, for example a BasicPolymorphicTypeValidator with an allow-list of permitted subtypes.

Workarounds

CNA: Configure an explicit restrictive PolymorphicTypeValidator rather than relying on the default validator, or avoid declaring java.lang.Comparable as the base type of an @JsonTypeInfo-annotated property or class. Narrowing the declared base type to an application-specific interface also removes the exposure.

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