CVE-2026-118445 in pybddisasm
Summary
by MITRE • 11/03/2026
A use-after-free vulnerability in the pybddisasm Python bindings affects structure-valued members of INSTRUX objects. These members are exposed through Python objects that reference memory owned by the parent INSTRUX object. A retained reference to a member does not keep the parent allocation alive. Accessing the member after the parent INSTRUX object has been freed therefore accesses freed memory. Depending on how the member is used and whether the freed allocation has been reused, this may expose process memory or cause the Python process to crash. Exploitation requires an application to retain and subsequently access a member reference after the parent object has been freed. The pybddisasm package is no longer maintained.
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified in the pybddisasm Python bindings represents a critical memory safety failure classified as a use-after-free condition, specifically impacting structure-valued members of INSTRUX objects. This flaw arises from an incorrect reference management strategy within the binding layer that interfaces between C++ code and the Python runtime environment. When an INSTRUX object is instantiated in C++, it allocates a block of memory to hold its structural data. The pybddisasm bindings expose specific fields or sub-structures of this parent object as separate Python objects to facilitate easier access for developers. However, these child Python objects do not maintain a strong reference count back to the parent INSTRUX allocation. Consequently, if the parent object is garbage collected and freed by the C++ side while a reference to one of its member structures remains active in the Python environment, the underlying memory backing that member becomes invalid.
From a technical perspective, this issue stems from a violation of ownership semantics typical in mixed-language environments where manual memory management coexists with automatic garbage collection. The parent object retains responsibility for freeing the allocated memory block upon destruction or explicit deallocation calls. Because the child objects do not increment the reference count of the parent allocation, they become dangling pointers once the parent is released. When an application subsequently attempts to read from or write to these member structures, it accesses memory that has already been returned to the system allocator. This scenario aligns with CWE-416, Use After Free, which describes situations where a program continues to use a pointer after it has been freed, leading to undefined behavior and potential security compromises.
The operational impact of this vulnerability is significant due to its potential for both information disclosure and denial of service. If the memory previously occupied by the INSTRUX object has not yet been reallocated or overwritten by other processes, accessing the dangling reference allows an attacker to read sensitive data from the process address space, potentially leaking cryptographic keys, session tokens, or internal application state. This capability maps directly to ATT&CK technique T1005, Data from Local System, which involves collecting data stored on local systems for later exfiltration. Alternatively, if the freed memory has been reused by other allocations with different structures or sizes, accessing it can lead to type confusion errors, buffer overflows during subsequent writes, or immediate segmentation faults that crash the Python interpreter. This aligns with ATT&CK technique T1429, Resource Hijacking, where availability is compromised through resource exhaustion via crashes.
Exploitation of this vulnerability requires a specific sequence of actions within an application using pybddisasm. The attacker must first trigger the creation and subsequent destruction of INSTRUX objects while retaining references to their internal member structures in Python variables or data structures. Once the parent object is garbage collected, any further interaction with these retained members triggers the use-after-free condition. Given that pybddisasm is a library used for binary disassembly and analysis, it may be employed in security tools, reverse engineering platforms, or automated malware analysis systems where large volumes of instruction objects are processed rapidly. The lack of active maintenance exacerbates the risk, as there are no official patches available to correct the reference counting logic.
Mitigation strategies must focus on immediate remediation through architectural changes and operational controls since a software patch is unavailable. Organizations relying on pybddisasm should immediately cease its use in production environments or sensitive analysis pipelines. The primary mitigation involves migrating to actively maintained alternatives such as Capstone, angr, or other disassembly libraries that have robust memory management practices and active community support for security issues. If migration is not immediately feasible, applications must implement strict lifecycle management policies where references to INSTRUX members are explicitly cleared before the parent object goes out of scope. This can be achieved by wrapping usage in context managers or explicit cleanup functions that nullify member references prior to triggering garbage collection of the parent. Additionally, deploying memory safety tools such as AddressSanitizer during development and testing phases can help detect similar issues in custom bindings before they reach production.