CVE-2026-22606 in fickling
Summary
by MITRE • 01/10/2026
Fickling is a Python pickling decompiler and static analyzer. Fickling versions up to and including 0.1.6 do not treat Python’s runpy module as unsafe. Because of this, a malicious pickle that uses runpy.run_path() or runpy.run_module() is classified as SUSPICIOUS instead of OVERTLY_MALICIOUS. If a user relies on Fickling’s output to decide whether a pickle is safe to deserialize, this misclassification can lead them to execute attacker-controlled code on their system. This affects any workflow or product that uses Fickling as a security gate for pickle deserialization. This issue has been patched in version 0.1.7.
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Analysis
by VulDB Data Team • 01/17/2026
The vulnerability identified as CVE-2026-22606 resides within the Fickling Python pickling decompiler and static analyzer, a tool designed to analyze and decompile Python pickle objects for security assessment purposes. This security flaw affects versions 0.1.6 and earlier, where the tool fails to properly classify certain malicious pickle payloads as overtly malicious, instead categorizing them as merely suspicious. The root cause stems from Fickling's insufficient handling of Python's built-in runpy module, which serves as a critical component for executing Python modules and scripts. The runpy module contains functions runpy.run_path() and runpy.run_module() that can execute arbitrary code when invoked through pickle deserialization, making them inherently dangerous when encountered in malicious contexts.
The technical flaw represents a critical misclassification issue within Fickling's security analysis engine, specifically related to its threat assessment algorithms. When processing pickle objects that utilize runpy module functions, the tool fails to recognize the full execution potential of these constructs, leading to a false positive in security assessment. This misclassification creates a dangerous gap in security workflows where systems relying on Fickling as a security gate may incorrectly determine that a malicious pickle payload is safe for deserialization. The vulnerability directly violates security principle 10 from the CWE taxonomy, which addresses improper handling of dangerous functions in security tools, and aligns with ATT&CK technique T1059.006 for "Command and Scripting Interpreter: Python" where adversaries leverage Python's module execution capabilities.
The operational impact of this vulnerability extends beyond simple code execution, as it fundamentally undermines the security posture of any system or workflow that depends on Fickling for pickle deserialization security checks. Attackers can craft malicious pickle objects that exploit the runpy module to execute arbitrary code on target systems without triggering proper security alerts. This creates a significant risk for applications that deserialize untrusted pickle data, particularly in environments where Fickling serves as an automated security gate. The vulnerability affects the broader Python ecosystem's security practices, as pickle deserialization remains a common pattern in many applications, making this flaw potentially widespread in scope. Organizations relying on Fickling for security validation may experience false negatives, where malicious payloads pass through security checks undetected, leading to potential system compromise.
Mitigation strategies for CVE-2026-22606 require immediate upgrading to Fickling version 0.1.7 or later, which properly addresses the misclassification issue. Security teams should also implement additional layers of protection for pickle deserialization workflows, including input validation, sandboxing mechanisms, and alternative security tools that properly handle runpy module functions. Organizations should conduct thorough security assessments of their existing pickle handling processes to identify potential exposure points. The fix implemented in version 0.1.7 likely involves enhanced signature detection for runpy module usage patterns and improved threat classification algorithms. Security practitioners should also consider implementing principle of least privilege controls around pickle deserialization operations and maintain comprehensive logging of all deserialization activities for incident response purposes. This vulnerability highlights the importance of maintaining up-to-date security tools and the critical need for proper threat assessment algorithms in static analysis tools.