8.1

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-41731

CVE-2026-41731: In Spring for Apache Kafka, overly broad trusted-package matching in header mappers exposes JDK classes to deserialization

JsonKafkaHeaderMapper and the deprecated DefaultKafkaHeaderMapper matched type headers against trusted packages using a prefix check, meaning that trusting any package implicitly trusted all of its subpackages. Combined with Jackson's default bean deserialization, a producer could supply crafted header values that caused the consumer to deserialize arbitrary JDK types.

Affected versions: Spring for Apache Kafka 4.0.0 through 4.0.5; 3.3.0 through 3.3.15; 3.2.0 through 3.2.13; 2.9.0 through 2.9.13; 2.8.0 through 2.8.11.

(GitHub Advisory)

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CVE-2026-41731

CVE-2026-41731:

8.1

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

SSVC / BOD 26-04 ↗

Exploitation NoneAutomatable NoTech Impact Total

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Package Name	Ecosystem	Vulnerable Versions	First Patched Version
org.springframework.kafka:spring-kafka	maven	>= 4.0.0, <= 4.0.5	4.0.6
org.springframework.kafka:spring-kafka	maven	>= 3.3.0, <= 3.3.15	3.3.16
org.springframework.kafka:spring-kafka	maven	>= 3.2.0, <= 3.2.13
org.springframework.kafka:spring-kafka	maven	>= 2.9.0, <= 2.9.13
org.springframework.kafka:spring-kafka	maven	<= 2.8.11

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability lies in the way Spring for Apache Kafka's JsonKafkaHeaderMapper and DefaultKafkaHeaderMapper handle trusted packages for deserialization. The root cause is the use of a startsWith check instead of an exact match when verifying if a package is trusted. This allows an attacker to craft a malicious header that points to a class in a subpackage of a trusted package, leading to the deserialization of arbitrary JDK types and potential remote code execution.

The analysis of the patch commits between the vulnerable and fixed versions clearly shows the removal of the startsWith logic in the isTrustedPackage method of both affected classes. The vulnerable functions are org.springframework.kafka.support.JsonKafkaHeaderMapper.isTrustedPackage and org.springframework.kafka.support.mapping.DefaultKafkaHeaderMapper.isTrustedPackage, as these are the methods containing the flawed logic that would be called during the deserialization process of a malicious Kafka message header.

Vulnerable functions

org.springframework.kafka.support.JsonKafkaHeaderMapper.isTrustedPackage

spring-kafka/src/main/java/org/springframework/kafka/support/JsonKafkaHeaderMapper.java

The `isTrustedPackage` method in `JsonKafkaHeaderMapper` used a `startsWith` check to validate if a package was trusted for deserialization. This allowed an attacker to bypass the trusted package restriction by providing a class from a subpackage of a trusted package. For example, if `com.example` was trusted, an attacker could use a class from `com.example.malicious` to trigger deserialization of arbitrary code. The patch fixes this by requiring an exact match of the package name.

org.springframework.kafka.support.mapping.DefaultKafkaHeaderMapper.isTrustedPackage

spring-kafka/src/main/java/org/springframework/kafka/support/mapping/DefaultKafkaHeaderMapper.java

Similar to `JsonKafkaHeaderMapper`, the `isTrustedPackage` method in the deprecated `DefaultKafkaHeaderMapper` also used a `startsWith` check for trusted packages. This exposed the same vulnerability, allowing deserialization of untrusted data. The patch removes the `startsWith` check and enforces an exact package name match.

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WAF Rule

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Reasoning

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