SEPTEMBER 17, 2026
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Case File

CVE-2026-83557

MEDIUM · CVSS 5.6 EPSS 0.59% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-09-01 · Last synced 2026-09-17

CyberRota Analysis

AI-Generated

The vulnerability affects the Jackson Databind library in Java, specifically related to the default handling of polymorphic type resolution when using the @JsonTypeInfo annotation without a custom validator. This flaw allows for the instantiation of attacker-controlled objects, potentially leading to path traversal vulnerabilities if the application processes the instantiated objects in a sensitive manner. Organizations utilizing affected versions of Jackson Databind should prioritize upgrading to the specified secure versions to mitigate the risk of exploitation.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
code execution

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-83557
Severity
MEDIUM
CVSS
5.6
EPSS
0.59%
Java

Original NVD Description

DefaultBaseTypeLimitingValidator is the PolymorphicTypeValidator applied automatically whenever @JsonTypeInfo is used without an explicitly configured custom validator. It denies polymorphic resolution only for a fixed set of "unsafe base types", and its isSafeSubType method returns true unconditionally for every base type outside that set. java.lang.Comparable was absent from the list despite being implemented by a very large fraction of JDK and application classes, comparable in breadth to java.io.Serializable, which is on the list for that reason. An application declaring an @JsonTypeInfo-annotated property or class with Comparable as its base type, and no custom PolymorphicTypeValidator, will accept a type identifier for essentially any class implementing Comparable. This yields an attacker-controlled object instantiation primitive; a demonstrated case constructs a java.io.File for an arbitrary attacker-chosen path, which becomes path-traversal-adjacent if the application subsequently calls path-sensitive methods on the value. No class implementing Comparable has been identified that yields code execution through deserialization alone. Global Default Typing via activateDefaultTyping is not affected, because that method structurally requires an explicit PolymorphicTypeValidator argument. This affects com.fasterxml.jackson.core:jackson-databind from 2.11.0 before 2.18.10, from 2.19.0 before 2.21.6, and from 2.22.0 before 2.22.2, and tools.jackson.core:jackson-databind from 3.0.0 before 3.1.6 and from 3.2.0 before 3.2.2. Users should upgrade to 2.18.10, 2.21.6, 2.22.2, 3.1.6, or 3.2.2.