detecting-arbitrary-write

name	detecting-arbitrary-write
description	Detects arbitrary write vulnerabilities by identifying unchecked array indexing and out-of-bounds memory writes. Use when analyzing memory write operations, pointer arithmetic, or investigating code execution vulnerabilities.

Arbitrary Write Detection

Detection Workflow

1. Identify write operations: Find all array writes, pointer dereference writes, format string usage with %n, struct member writes
2. Trace input sources: Use xrefs_to to trace input, follow user data to write points, identify attacker-controlled values
3. Check bounds validation: Verify array bounds checks, assess pointer arithmetic safety, check format string validation, review type safety
4. Assess exploitability: Can attacker control write address? Can attacker control write value? What can be overwritten? Can code execution be achieved?

Key Patterns

• Unchecked array indexing: array writes with user-controlled indices, pointer arithmetic writes with user input
• Format string writes: user-controlled format strings with %n, memory writes via printf
• Pointer dereference writes: writing through user-controlled pointers, use-after-free writes, vtable corruption
• Struct/class member writes: writing to wrong struct members, type confusion, vtable/function pointer overwrites

Output Format

Report with: id, type, subtype, severity, confidence, location, vulnerability, write operation, array base, index source, value source, bounds check, exploitable, attack scenario, potential targets, mitigation.

Severity Guidelines

• CRITICAL: Arbitrary write enabling code execution
• HIGH: Arbitrary write with significant impact
• MEDIUM: Arbitrary write with limited impact
• LOW: Minor arbitrary write issues

See Also

• patterns.md - Detailed detection patterns and exploitation scenarios
• examples.md - Example analysis cases and code samples
• references.md - CWE references and mitigation strategies