fix: remove unsafe exec() in stratifier.c

[orbisai0security]

Summary

Fix critical severity security issue in src/stratifier.c.

Vulnerability

Field	Value
ID	V-010
Severity	CRITICAL
Scanner	multi_agent_ai
Rule	V-010
File	src/stratifier.c:506
CWE	CWE-120

Description: The combination of heap buffer overflows (V-001), integer overflows (V-002), and double-free vulnerabilities (V-003) in stratifier.c creates a complete exploitation chain for remote code execution. An attacker can craft a sequence of stratum protocol messages or malicious Bitcoin node responses that: (1) trigger an integer overflow causing malloc to allocate an undersized buffer, (2) overflow that buffer via unchecked memcpy to corrupt heap metadata, (3) trigger a double-free to corrupt the tcache free list, and (4) use a subsequent malloc to obtain a pointer to attacker-controlled memory, achieving an arbitrary write primitive. This enables overwriting a function pointer or GOT entry to redirect execution to attacker shellcode or a ROP chain. If the binary is not compiled with PIE, fixed addresses eliminate the need to bypass ASLR.

Changes

• src/stratifier.c

Verification

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

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Automated security fix by OrbisAI Security