FKIE_CVE-2026-83557
Vulnerability from fkie_nvd - Published: 2026-09-01 15:17 - Updated: 2026-09-01 18:17
Severity
Summary
DefaultBaseTypeLimitingValidator 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.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"collectionURL": "https://repo.maven.apache.org/maven2",
"defaultStatus": "unaffected",
"packageName": "com.fasterxml.jackson.core:jackson-databind",
"product": "jackson-databind",
"programFiles": [
"src/main/java/com/fasterxml/jackson/databind/jsontype/DefaultBaseTypeLimitingValidator.java"
],
"programRoutines": [
{
"name": "com.fasterxml.jackson.databind.jsontype.DefaultBaseTypeLimitingValidator.isUnsafeBaseType"
}
],
"repo": "https://github.com/FasterXML/jackson-databind",
"vendor": "FasterXML",
"versions": [
{
"lessThan": "2.18.10",
"status": "affected",
"version": "2.11.0",
"versionType": "maven"
},
{
"lessThan": "2.21.6",
"status": "affected",
"version": "2.19.0",
"versionType": "maven"
},
{
"lessThan": "2.22.2",
"status": "affected",
"version": "2.22.0",
"versionType": "maven"
}
]
},
{
"collectionURL": "https://repo.maven.apache.org/maven2",
"defaultStatus": "unaffected",
"packageName": "tools.jackson.core:jackson-databind",
"product": "jackson-databind",
"programFiles": [
"src/main/java/tools/jackson/databind/jsontype/DefaultBaseTypeLimitingValidator.java"
],
"programRoutines": [
{
"name": "tools.jackson.databind.jsontype.DefaultBaseTypeLimitingValidator.isUnsafeBaseType"
}
],
"repo": "https://github.com/FasterXML/jackson-databind",
"vendor": "FasterXML",
"versions": [
{
"lessThan": "3.1.6",
"status": "affected",
"version": "3.0.0",
"versionType": "maven"
},
{
"lessThan": "3.2.2",
"status": "affected",
"version": "3.2.0",
"versionType": "maven"
}
]
}
],
"source": "36c7be3b-2937-45df-85ea-ca7133ea542c"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "DefaultBaseTypeLimitingValidator 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."
}
],
"id": "CVE-2026-83557",
"lastModified": "2026-09-01T18:17:47.387",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "LOW",
"baseScore": 5.6,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "LOW",
"integrityImpact": "LOW",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L",
"version": "3.1"
},
"exploitabilityScore": 2.2,
"impactScore": 3.4,
"source": "36c7be3b-2937-45df-85ea-ca7133ea542c",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-83557",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-01T17:46:23.527612Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-09-01T15:17:37.987",
"references": [
{
"source": "36c7be3b-2937-45df-85ea-ca7133ea542c",
"url": "https://github.com/FasterXML/jackson-databind/commit/eb3b7fc0f9c0d27f471550ac3316b17d1987388f"
},
{
"source": "36c7be3b-2937-45df-85ea-ca7133ea542c",
"url": "https://github.com/FasterXML/jackson-databind/issues/6156"
},
{
"source": "36c7be3b-2937-45df-85ea-ca7133ea542c",
"url": "https://github.com/FasterXML/jackson-databind/pull/6155"
},
{
"source": "36c7be3b-2937-45df-85ea-ca7133ea542c",
"url": "https://github.com/FasterXML/jackson-databind/security/advisories/GHSA-gx83-3vf8-gh7j"
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"url": "https://github.com/FasterXML/jackson-databind/security/advisories/GHSA-gx83-3vf8-gh7j"
}
],
"sourceIdentifier": "36c7be3b-2937-45df-85ea-ca7133ea542c",
"vulnStatus": "Received",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-502"
},
{
"lang": "en",
"value": "CWE-915"
}
],
"source": "36c7be3b-2937-45df-85ea-ca7133ea542c",
"type": "Secondary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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