Unsafe Pickle Deserialization in Picklescan

Executive Summary

CVE-2026-56304 is a vulnerability in the picklescan package versions before 1.0.1 that involves unsafe pickle deserialization.

This flaw allows unauthenticated attackers to create arbitrary zero-byte files on the server by exploiting the logging.FileHandler class from Python's standard library.

Attackers craft malicious pickle payloads that bypass Remote Code Execution (RCE) blocklists and cause the creation of empty files, such as lock files, which can disrupt application logic or cause denial of service.

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Impact Analysis

The vulnerability can lead to the creation of arbitrary zero-byte files anywhere on the filesystem where the application has write permissions.

This can cause filesystem pollution or logic disruption, for example by creating lock files that prevent the application from starting.

As a result, it may cause denial of service (DoS) or application disruption, impacting availability and reliability.

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Detection Guidance

This vulnerability involves the creation of arbitrary zero-byte files via unsafe pickle deserialization using the logging.FileHandler class. Detection can focus on identifying unexpected zero-byte files or lock files created in the filesystem, which may indicate exploitation attempts.

You can search for zero-byte files or suspicious lock files in directories used by the picklescan application or related services. For example, on a Unix-like system, you might use commands like:

• find /path/to/application -type f -size 0
• find /path/to/application -name '*.lock'

Additionally, monitoring logs for unusual pickle deserialization attempts or unexpected instantiations of logging.FileHandler objects could help detect exploitation, but specific commands for this are not provided in the available resources.

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Mitigation Strategies

The primary mitigation step is to upgrade the picklescan package to version 1.0.1 or later, where this unsafe pickle deserialization vulnerability has been fixed.

Until an upgrade can be applied, consider restricting or monitoring the use of pickle deserialization in your environment, especially where untrusted data might be processed.

Also, monitor and clean up any zero-byte files or lock files created by exploitation attempts to prevent denial of service or application disruption.

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Compliance Impact

The provided information does not specify any direct impact of CVE-2026-56304 on compliance with common standards and regulations such as GDPR or HIPAA.

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