Deserialization Flaw in Apache Airflow XCom API

Executive Summary

This vulnerability in Apache Airflow allows an authenticated user with XCom write-and-read access to bypass security checks and instantiate arbitrary classes on the API server. It occurs when a user writes an XCom value and reads it back with deserialize=true, triggering unsafe class instantiation via a string-literal payload.

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Detection Guidance

To detect this vulnerability, check Apache Airflow logs for unauthorized XCom deserialization attempts. Look for requests to the /api/v2/{...}/xcomEntries/{key} endpoint with deserialize=true parameter. Monitor for errors related to class instantiation or reserved key usage in XCom values.

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Impact Analysis

An attacker could exploit this to execute arbitrary code on the Airflow server, potentially leading to data breaches, unauthorized access, or system compromise. It requires authenticated API access with XCom permissions.

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Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality principles or HIPAA's security requirements for protected health information. Compliance may be compromised if exploited.

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Mitigation Strategies

Upgrade Apache Airflow to version 3.3.1 or later immediately. This version includes the fix that rejects reserved XCom serialization keys even when submitted as JSON string literals. Temporarily restrict API access to trusted users until the upgrade is completed.

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