CVE-2026-88350 in MPack
Summary
by MITRE • 09/22/2026
An integer overflow vulnerability exists in MPack 1.1.1 in mpack_node_cstr_alloc() and mpack_node_utf8_cstr_alloc().
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/22/2026
The presence of an integer overflow vulnerability within the MPack library version 1.1.1, specifically affecting the functions mpack_node_cstr_alloc and mpack_node_utf8_cstr_alloc, represents a critical security flaw that compromises memory safety during string allocation operations. These functions are designed to allocate memory for null-terminated C strings derived from MessagePack nodes, which is a common step when converting binary data into human-readable text formats within applications utilizing this serialization library. The vulnerability arises because the calculation determining the size of the buffer required for these allocations fails to properly account for potential arithmetic overflows before invoking standard allocation routines such as malloc or realloc. When an attacker supplies crafted input that results in a calculated size exceeding the maximum value representable by the integer type used, the result wraps around to a small positive number rather than triggering an error condition.
This mathematical flaw leads directly to a heap-based buffer overflow scenario where significantly less memory is allocated than what subsequent operations attempt to write into it. The operational impact of this vulnerability is severe, as writing beyond the bounds of the allocated heap buffer can corrupt adjacent data structures, overwrite function pointers, or alter control flow mechanisms stored in nearby memory regions. In practical terms, an attacker who can influence the input processed by these specific functions could potentially achieve arbitrary code execution with the privileges of the affected application process. This is particularly dangerous because MPack is often embedded within high-performance network services, game servers, and configuration management tools where it handles untrusted or semi-trusted data streams from external sources.
From a classification perspective, this vulnerability aligns closely with CWE-190, which defines integer overflow or wraparound errors that lead to subsequent memory corruption issues such as buffer overflows. The attack vector typically involves the exploitation of input validation weaknesses where the application fails to verify that the size parameter passed to allocation functions remains within safe bounds relative to the maximum allowable heap allocation for the platform architecture. This aligns with ATT&CK technique T1203, which covers Exploitation for Client Execution, as well as general patterns found in CWE-787 related to out-of-bounds writes on heap structures. The lack of explicit checks for integer overflow prior to memory allocation is a common oversight in C and C++ codebases that prioritize performance over rigorous bounds checking during dynamic resource management phases.
Mitigation strategies must focus on both immediate patching and long-term defensive coding practices. Organizations relying on MPack 1.1.1 should immediately upgrade to the latest patched version where these specific functions have been updated to include explicit integer overflow checks before proceeding with memory allocation. Developers integrating this library into their codebases should also implement input validation layers that sanitize or limit the size of string data derived from MessagePack nodes, ensuring that no single node can request an excessively large buffer relative to available system resources. Furthermore, adopting static analysis tools capable of detecting potential integer overflows during the compilation phase and utilizing dynamic memory sanitizers like AddressSanitizer in testing environments can help identify similar latent vulnerabilities across the entire codebase before deployment into production environments.