CVE-2022-4996 in mruby
Summary
by MITRE • 08/20/2026
A flaw has been found in mruby 3.1.0. Affected is the function udiv of the file bigint.c. Executing a manipulation can lead to floating point comparison with incorrect operator. It is possible to launch the attack remotely. The exploit has been published and may be used. It is best practice to apply a patch to resolve this issue.
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Analysis
by VulDB Data Team • 08/24/2026
The vulnerability identified in mruby version 3.1.0 represents a critical logic error within the big integer arithmetic implementation, specifically located in the udiv function found in the bigint.c source file. This flaw stems from an incorrect floating-point comparison operator being utilized during division operations involving large integers. In high-precision numerical computing environments such as those provided by mruby's arbitrary precision library, accurate handling of edge cases and boundary conditions is paramount for maintaining data integrity. The specific defect involves a scenario where the algorithm relies on floating-point approximations to determine quotient digits or remainder values. Due to the inherent imprecision of IEEE 754 floating-point arithmetic when dealing with very large numbers that exceed standard double-precision mantissa limits, the comparison logic fails to correctly identify equality or inequality states in certain edge cases. This results in a deviation from the expected mathematical result, leading to incorrect computation outcomes rather than immediate memory corruption or crashes, although such miscalculations can cascade into further logical errors within dependent applications.
From an operational perspective, this vulnerability poses significant risks to any application relying on mruby for financial calculations, cryptographic parameter generation, or scientific simulations where numerical accuracy is non-negotiable. An attacker who can influence the inputs passed to the udiv function may induce these incorrect comparisons, thereby manipulating the output of arithmetic operations. Since the exploit has been published and demonstrated publicly, the window for unpatched systems is effectively closed against targeted attacks. The ability to launch this attack remotely implies that if mruby is exposed via a network service or web application interface without proper input validation or sandboxing, an external adversary can trigger these erroneous computations. This could lead to data corruption, incorrect decision-making processes in automated systems, or potentially bypass security checks that rely on precise numerical comparisons for authorization or integrity verification.
The technical classification of this flaw aligns with CWE-682, which covers Incorrect Calculation, and more specifically relates to issues arising from improper handling of numeric precision and comparison logic. In the context of the MITRE ATT&CK framework, this vulnerability facilitates techniques associated with Data Manipulation (T1565) or potentially Impact-related tactics if the incorrect calculations lead to system state changes that disrupt service availability or integrity. The root cause is not a memory safety issue like buffer overflow but rather a logical flaw in algorithmic implementation where floating-point approximations are used unsafely for exact integer arithmetic verification. This highlights the danger of mixing approximate and exact numerical methods without rigorous boundary testing, particularly when dealing with numbers that approach the limits of representable precision.
To mitigate this vulnerability, immediate action is required to apply the official patch released by the mruby maintainers. Organizations running mruby 3.1.0 should upgrade to a patched version where the udiv function has been corrected to use exact integer arithmetic or robust comparison methods that do not rely on potentially imprecise floating-point operations for critical decision points within the division algorithm. Additionally, developers integrating mruby into larger systems should implement strict input validation and sanitization routines to limit the range of values passed to big integer functions, reducing the attack surface even if patching is delayed temporarily. It is also advisable to review application logic that depends on precise numerical outputs from mruby for potential side effects caused by this flaw in unpatched environments. Regular security audits focusing on mathematical libraries and continuous integration testing with edge-case inputs are recommended best practices to prevent similar logical errors in future development cycles.