FasterXML jackson-databind up to 3.2.1 DefaultBaseTypeLimitingValidator isSafeSubType deserialization

Summaryinfo

A vulnerability, which was classified as critical, has been found in FasterXML jackson-databind up to 2.18.9/2.21.5/2.22.1/3.1.5/3.2.1. Impacted is the function isSafeSubType of the component DefaultBaseTypeLimitingValidator. This manipulation causes deserialization. The identification of this vulnerability is CVE-2026-83557. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in FasterXML jackson-databind up to 2.18.9/2.21.5/2.22.1/3.1.5/3.2.1. It has been declared as critical. Affected by this vulnerability is the function isSafeSubType of the component DefaultBaseTypeLimitingValidator. The manipulation with an unknown input leads to a deserialization vulnerability. The CWE definition for the vulnerability is CWE-502. The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-83557 since 08/31/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 2.18.10, 2.21.6, 2.22.2, 3.1.6 or 3.2.2 eliminates this vulnerability.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Programming Language Software

Vendor

• FasterXML

Name

• jackson-databind

Version

• 2.18.0
• 2.18.1
• 2.18.2
• 2.18.3
• 2.18.4
• 2.18.5
• 2.18.6
• 2.18.7
• 2.18.8
• 2.18.9
• 2.21.0
• 2.21.1
• 2.21.2
• 2.21.3
• 2.21.4
• 2.21.5
• 2.22.0
• 2.22.1
• 3.1.0
• 3.1.1
• 3.1.2
• 3.1.3
• 3.1.4
• 3.1.5
• 3.2.0
• 3.2.1

License

• open-source

Website

• Product: https://github.com/FasterXML/jackson-databind/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion