Type Confusion in Jackson Databind

Executive Summary

The vulnerability exists in jackson-databind's BasicPolymorphicTypeValidator.Builder.allowIfSubTypeIsArray() method. This method allowlists any array type based solely on whether the class is an array, without validating the array's component (element) type against the configured allowlist.

As a result, even if there is an explicit allowlist of concrete types, an array of a disallowed type (e.g., EvilType[]) can still be deserialized. When Jackson deserializes such arrays and no per-element type IDs are present, it directly instantiates the component type without further checks, effectively bypassing the allowlist.

This flaw allows potentially unsafe types to be deserialized, which can lead to security issues.

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Impact Analysis

This vulnerability can lead to the deserialization of unauthorized or malicious types, which may result in remote code execution or other severe security impacts.

Because the vulnerability allows instantiation of disallowed types, attackers could exploit it to execute arbitrary code, compromise data integrity, or cause denial of service.

The CVSS score of 8.1 indicates a high severity with impacts on confidentiality, integrity, and availability.

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Mitigation Strategies

To mitigate this vulnerability, you should upgrade jackson-databind to one of the fixed versions: 2.18.8, 2.21.4, or 3.1.4.

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Compliance Impact

CVE-2026-54513 is a high severity vulnerability (CVSS 8.1) in the jackson-databind library that allows bypassing type validation during deserialization, potentially enabling attackers to instantiate arbitrary classes. This can lead to unauthorized code execution or data manipulation.

Such a vulnerability can impact compliance with common standards and regulations like GDPR and HIPAA because it threatens the confidentiality, integrity, and availability of sensitive data processed by applications using the affected library.

If exploited, attackers could gain unauthorized access or modify protected data, violating data protection requirements and potentially leading to breaches of regulatory obligations.

Therefore, organizations using vulnerable versions of jackson-databind may face increased risk of non-compliance with data security standards until the vulnerability is remediated.

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Detection Guidance

This vulnerability is related to the Jackson Databind library's deserialization process, specifically in the BasicPolymorphicTypeValidator's handling of array subtypes. Detection typically involves identifying usage of vulnerable versions of jackson-databind (from 2.10.0 up to but not including 2.18.8, 2.21.4, and 3.1.4) in your software stack.

To detect if your system is vulnerable, you can check the version of jackson-databind used by your applications. For example, if you have access to the deployed Java application or its dependencies, you can run commands like:

• Using Maven dependency tree: mvn dependency:tree | grep jackson-databind
• Using Gradle dependencies: ./gradlew dependencies | grep jackson-databind
• Checking the jar manifest or file name for version info: unzip -p jackson-databind.jar META-INF/MANIFEST.MF | grep Implementation-Version

Additionally, to detect exploitation attempts on your network, you can monitor for suspicious deserialization payloads that attempt to instantiate disallowed classes wrapped in arrays. However, no specific network detection commands or signatures are provided in the available resources.

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