Vulnerability-Lookup

CVE-2026-54512 (GCVE-0-2026-54512)

Vulnerability from cvelistv5 – Published: 2026-06-23 20:56 – Updated: 2026-06-23 20:56

Title

jackson-databind: PolymorphicTypeValidator bypass via generic type parameters allows arbitrary class instantiation

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.

Severity

8.1 (High)


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

CWE

CWE-184 - Incomplete List of Disallowed Inputs
CWE-502 - Deserialization of Untrusted Data

Assigner

GitHub_M

References

3 references

URL	Tags
https://github.com/FasterXML/jackson-databind/sec…	x_refsource_CONFIRM
https://github.com/FasterXML/jackson-databind/iss…	x_refsource_MISC
https://github.com/FasterXML/jackson-databind/com…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
FasterXML	jackson-databind	Affected: >= 2.10.0, < 2.18.8 Affected: >= 2.19.0, < 2.21.4 Affected: >= 3.0.0, < 3.1.4

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JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "jackson-databind",
          "vendor": "FasterXML",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.10.0, \u003c 2.18.8"
            },
            {
              "status": "affected",
              "version": "\u003e= 2.19.0, \u003c 2.21.4"
            },
            {
              "status": "affected",
              "version": "\u003e= 3.0.0, \u003c 3.1.4"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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\u0027s 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 \u003c), DatabindContext._resolveAndValidateGeneric() validates only the raw container class name (the substring before \u003c) 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 \u2014 for example java.util.ArrayList\u003ccom.evil.Gadget\u003e 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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-184",
              "description": "CWE-184: Incomplete List of Disallowed Inputs",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-502",
              "description": "CWE-502: Deserialization of Untrusted Data",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-23T20:56:36.646Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/FasterXML/jackson-databind/security/advisories/GHSA-j3rv-43j4-c7qm",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/FasterXML/jackson-databind/security/advisories/GHSA-j3rv-43j4-c7qm"
        },
        {
          "name": "https://github.com/FasterXML/jackson-databind/issues/5988",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/FasterXML/jackson-databind/issues/5988"
        },
        {
          "name": "https://github.com/FasterXML/jackson-databind/commit/434d6c511de7fdd9872f29157aafb6162d12d8d5",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/FasterXML/jackson-databind/commit/434d6c511de7fdd9872f29157aafb6162d12d8d5"
        }
      ],
      "source": {
        "advisory": "GHSA-j3rv-43j4-c7qm",
        "discovery": "UNKNOWN"
      },
      "title": "jackson-databind: PolymorphicTypeValidator bypass via generic type parameters allows arbitrary class instantiation"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-54512",
    "datePublished": "2026-06-23T20:56:36.646Z",
    "dateReserved": "2026-06-15T18:01:15.513Z",
    "dateUpdated": "2026-06-23T20:56:36.646Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-J3RV-43J4-C7QM

Vulnerability from github – Published: 2026-06-23 21:21 – Updated: 2026-06-23 21:21

Summary

jackson-databind has a PolymorphicTypeValidator bypass via generic type parameters that allows arbitrary class instantiation

Details

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 is the same vulnerability class responsible for the historical sequence of jackson-databind deserialization CVEs; here it manifests as a validator bypass rather than a missing deny-list entry.

Impact

Bypass of the PTV allow-list, including the recommended BasicPolymorphicTypeValidator configured with name-prefix allow rules.
Arbitrary class instantiation of any type assignable to the container's element/parameter position, with attacker-controlled property values (setter/field injection).
Potential unauthenticated remote code execution when a class with exploitable side effects (JNDI lookup, JDBC/connection-pool gadgets,TemplatesImpl-style loaders, etc.) is present on the classpath.

Applications that accept untrusted JSON and rely on a configured PTV — the documented, security-conscious configuration — are affected.

Proof of Concept

Configuration restricting polymorphic deserialization to a single safe container:

BasicPolymorphicTypeValidator ptv = BasicPolymorphicTypeValidator.builder()
        .allowIfSubType("java.util.ArrayList")
        .build();

ObjectMapper mapper = JsonMapper.builder()
        .polymorphicTypeValidator(ptv)
        .build();

Malicious payload (Wrapper.value is Object with @JsonTypeInfo(use = Id.CLASS, include = As.WRAPPER_ARRAY)):

{"value":["java.util.ArrayList<com.evil.EvilGadget>",[{"cmd":"calc.exe"}]]}

On vulnerable versions, com.evil.EvilGadget is instantiated and its cmd property is set, despite only java.util.ArrayList being allow-listed. On 2.18.8 / 2.21.4 / 3.1.4 the deserialization throws InvalidTypeIdException before instantiation.

Variant payloads (all bypass an ArrayList/HashMap allow-list):

Type ID	Smuggled type position
`java.util.ArrayList<Evil>`	list element
`java.util.HashMap<Evil,String>`	map key
`java.util.HashMap<String,Evil>`	map value
`java.util.ArrayList<java.util.ArrayList<Evil>>`	nested element
`java.util.ArrayList<Evil[]>`	array element

Patches

Fixed in 2.18.8, 2.21.4 and 3.1.4 via the changes for FasterXML/jackson-databind#5988, commit 434d6c511. The fix adds recursive validation of each non-trivial type parameter (and array element types appearing as parameters) through the full PTV chain, with documented exemptions for Object (wildcard resolution) and Enum types.

PolymorphicTypeValidator was added in 2.10.0 so vulnerability N/A for versions prior to that.

Severity

8.1 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.18.7"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "com.fasterxml.jackson.core:jackson-databind"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.10.0"
            },
            {
              "fixed": "2.18.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.1.3"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "com.fasterxml.jackson.core:jackson-databind"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.1.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.21.3"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "com.fasterxml.jackson.core:jackson-databind"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.19.0"
            },
            {
              "fixed": "2.21.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.1.3"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "tools.jackson.core:jackson-databind"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.1.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54512"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-184",
      "CWE-502"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-23T21:21:38Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "`jackson-databind`\u0027s `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 `\u003c`), `DatabindContext._resolveAndValidateGeneric()` validates **only the raw container class name** (the substring before `\u003c`) against the configured PTV.\n\nIf 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.\n\nAn attacker who controls the type ID can therefore place a denied class as a generic type parameter of an allowed container \u2014 for example `java.util.ArrayList\u003ccom.evil.Gadget\u003e` 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.\n\nThis is the same vulnerability class responsible for the historical sequence of jackson-databind deserialization CVEs; here it manifests as a validator bypass rather than a missing deny-list entry.\n\n\n## Impact\n\n- **Bypass of the PTV allow-list**, including the recommended `BasicPolymorphicTypeValidator` configured with name-prefix allow rules.\n- **Arbitrary class instantiation** of any type assignable to the container\u0027s element/parameter position, with attacker-controlled property values (setter/field injection).\n- **Potential unauthenticated remote code execution** when a class with exploitable side effects (JNDI lookup, JDBC/connection-pool gadgets,`TemplatesImpl`-style loaders, etc.) is present on the classpath.\n\nApplications that accept untrusted JSON and rely on a configured PTV \u2014 the documented, security-conscious configuration \u2014 are affected.\n\n\n## Proof of Concept\n\nConfiguration restricting polymorphic deserialization to a single safe container:\n\n```java\nBasicPolymorphicTypeValidator ptv = BasicPolymorphicTypeValidator.builder()\n        .allowIfSubType(\"java.util.ArrayList\")\n        .build();\n\nObjectMapper mapper = JsonMapper.builder()\n        .polymorphicTypeValidator(ptv)\n        .build();\n```\n\nMalicious payload (`Wrapper.value` is `Object` with `@JsonTypeInfo(use = Id.CLASS, include = As.WRAPPER_ARRAY)`):\n\n```json\n{\"value\":[\"java.util.ArrayList\u003ccom.evil.EvilGadget\u003e\",[{\"cmd\":\"calc.exe\"}]]}\n```\n\nOn vulnerable versions, `com.evil.EvilGadget` is instantiated and its `cmd` property is set, despite only `java.util.ArrayList` being allow-listed. On `2.18.8` / `2.21.4` / `3.1.4` the deserialization throws `InvalidTypeIdException` before instantiation.\n\n**Variant payloads** (all bypass an `ArrayList`/`HashMap` allow-list):\n\n| Type ID | Smuggled type position |\n|---|---|\n| `java.util.ArrayList\u003cEvil\u003e` | list element |\n| `java.util.HashMap\u003cEvil,String\u003e` | map key |\n| `java.util.HashMap\u003cString,Evil\u003e` | map value |\n| `java.util.ArrayList\u003cjava.util.ArrayList\u003cEvil\u003e\u003e` | nested element |\n| `java.util.ArrayList\u003cEvil[]\u003e` | array element |\n\n---\n\n## Patches\n\nFixed in **2.18.8**, **2.21.4** and **3.1.4** via the changes for [FasterXML/jackson-databind#5988](https://github.com/FasterXML/jackson-databind/issues/5988), commit `434d6c511`. The fix adds recursive validation of each non-trivial type parameter (and array element types appearing as parameters) through the full PTV chain, with documented exemptions for `Object` (wildcard resolution) and `Enum` types.\n\n`PolymorphicTypeValidator` was added in 2.10.0 so vulnerability N/A for versions prior to that.",
  "id": "GHSA-j3rv-43j4-c7qm",
  "modified": "2026-06-23T21:21:38Z",
  "published": "2026-06-23T21:21:38Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-databind/security/advisories/GHSA-j3rv-43j4-c7qm"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-databind/issues/5988"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-databind/commit/434d6c511de7fdd9872f29157aafb6162d12d8d5"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/FasterXML/jackson-databind"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "jackson-databind has a PolymorphicTypeValidator bypass via generic type parameters that allows arbitrary class instantiation"
}

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.

Detection rules are retrieved from Rulezet.

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