Deserialization of Untrusted Data Affecting tools.jackson.core:jackson-databind package, versions [,3.1.6)[3.2.0,3.2.2)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-JAVA-TOOLSJACKSONCORE-19496767
- published2 Sept 2026
- disclosed1 Sept 2026
- creditprvazsahnazarov
Introduced: 1 Sep 2026
NewCVE-2026-83557 (opens in a new tab)How to fix?
Upgrade tools.jackson.core:jackson-databind to version 3.1.6, 3.2.2 or higher.
Overview
Affected versions of this package are vulnerable to Deserialization of Untrusted Data in the isSafeSubType() method of DefaultBaseTypeLimitingValidator, whose denylist of unsafe base types omits java.lang.Comparable, so the method returns true for any subtype resolved under a Comparable base. An attacker can trigger instantiation of arbitrary classes that implement Comparable, such as java.io.File to reach path-traversal primitives, by sending JSON with attacker-controlled type identifiers. This requires the application to use a bare @JsonTypeInfo with the default validator and no explicit PolymorphicTypeValidator, and a property or class whose declared base type is Comparable.
Workaround
This vulnerability can be avoided by configuring an explicit restrictive PolymorphicTypeValidator, such as a BasicPolymorphicTypeValidator allowlist passed to activateDefaultTyping(), instead of relying on the default validator.
Note: The discoverer of this vulnerability reports that "I have not identified a class implementing Comparable that yields code execution purely through deserialization".
Details
Serialization is a process of converting an object into a sequence of bytes which can be persisted to a disk or database or can be sent through streams. The reverse process of creating object from sequence of bytes is called deserialization. Serialization is commonly used for communication (sharing objects between multiple hosts) and persistence (store the object state in a file or a database). It is an integral part of popular protocols like Remote Method Invocation (RMI), Java Management Extension (JMX), Java Messaging System (JMS), Action Message Format (AMF), Java Server Faces (JSF) ViewState, etc.
Deserialization of untrusted data (CWE-502) is when the application deserializes untrusted data without sufficiently verifying that the resulting data will be valid, thus allowing the attacker to control the state or the flow of the execution.