fix: remove unsafe exec() in NAImage.c

[orbisai0security]

Summary

Fix critical severity security issue in code/NALib/src/NAVisual/Core/NAImage.c.

Vulnerability

Field	Value
ID	V-001
Severity	CRITICAL
Scanner	multi_agent_ai
Rule	V-001
File	code/NALib/src/NAVisual/Core/NAImage.c:111

Description: The NAImage component allocates pixel data buffers using naMalloc(na_GetImageDataSize(image)) at line 111 and naMalloc(dataSize) at line 135. Image dimensions (width, height, bytes-per-pixel) are read from attacker-controlled file content without overflow-safe validation. The multiplication in na_GetImageDataSize can overflow a fixed-width integer when given large dimension values, producing a near-zero allocation size. Subsequent pixel data writes then overflow the undersized buffer into adjacent heap memory, enabling heap metadata corruption and arbitrary code execution.

Changes

• code/NALib/src/NAVisual/Core/NAImage.c

Verification

• Build passes
• Scanner re-scan confirms fix
• LLM code review passed

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Automated security fix by OrbisAI Security