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jackson-databind's renamed @JsonIgnore'd setters can deserialize via private fields

Moderate severity GitHub Reviewed Published Jun 16, 2026 in FasterXML/jackson-databind • Updated Jun 23, 2026

Package

maven com.fasterxml.jackson.core:jackson-databind (Maven)

Affected versions

>= 2.21.0, < 2.21.4
>= 3.0.0, < 3.1.4

Patched versions

2.21.4
3.1.4
maven tools.jackson.core:jackson-databind (Maven)
>= 3.0.0, < 3.1.4
3.1.4

Description

Summary

POJOPropertiesCollector._renameProperties() allows a property with @JsonProperty("renamed") on the getter and @JsonIgnore on the setter to be renamed rather than dropped. With MapperFeature.INFER_PROPERTY_MUTATORS enabled (default), the private backing field is retained; during deserialization BeanDeserializerFactory.addBeanProps() sees hasField()==true, builds a FieldProperty, and makes the backing field writable. An attacker supplying the renamed JSON key writes the backing field directly, bypassing the @JsonIgnore on the setter.

Impact

POJOs combining a renamed getter with an ignored setter (a read-only-over-the-wire pattern) have that field silently set from attacker input (property tampering / mass assignment). Not a general gadget; no RCE.

Affected / Patched (verified via git tag --contains)

  • 2.21 line: >= 2.21.0, < 2.21.4 -> fixed in 2.21.4 (backport c3d56dd, #5968)
  • 3.x line: >= 3.0.0, < 3.1.4 -> fixed in 3.1.4 (#5967, e88cb17)

Severity / CWE

Maintainer: minor. Reporter: HIGH. CWE-915.

Credits

Omkhar Arasaratnam (@omkhar) - finder.

References

@cowtowncoder cowtowncoder published to FasterXML/jackson-databind Jun 16, 2026
Published to the GitHub Advisory Database Jun 23, 2026
Reviewed Jun 23, 2026
Last updated Jun 23, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(20th percentile)

Weaknesses

Improperly Controlled Modification of Dynamically-Determined Object Attributes

The product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified. Learn more on MITRE.

CVE ID

CVE-2026-54516

GHSA ID

GHSA-9fxm-vc8v-hj55

Source code

Credits

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