detecting-null-pointer-dereference

Testing & Quality

Detects null pointer dereference vulnerabilities by identifying unchecked pointer usage and missing validation. Use when analyzing pointer operations, input validation, or investigating crash vulnerabilities.

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Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/data/detecting-null-pointer-dereference/SKILL.md

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Null Pointer Dereference Detection

Detection Workflow

Identify pointer dereferences: Find all pointer dereferences (*ptr, ptr->field), array accesses (ptr[index]), function calls with pointer parameters, pointer operations
Trace pointer sources: Use xrefs_to to trace pointers, find where pointers originate, identify pointer assignments, track pointer values
Check null validation: Verify null checks before dereference, assess check completeness, identify missing validation paths, check validation logic correctness
Assess impact: Can attacker control pointer value? Is dereference reachable? What's the crash potential? Can it lead to security issues?

Key Patterns

Missing null checks: pointer dereference without null check, function calls with unchecked pointers, array access through null pointers, member access through null pointers
Conditional dereference: dereference after partial null check, dereference in only some code paths, dereference after pointer assignment, dereference in loop conditions
Function parameter issues: unchecked function parameters, assumptions about non-null parameters, missing validation in public APIs, null pointers from external sources
Return value issues: dereferencing potentially null return values, assuming malloc/new never returns null, missing checks on function returns, dereferencing failed allocations

Output Format

Report with: id, type, subtype, severity, confidence, location, dereferenced_pointer, dereference_type, dereference_operation, pointer_source, null_check, vulnerability, exploitable, attack_scenario, impact, mitigation.

Severity Guidelines

HIGH: Null dereference in critical code paths
MEDIUM: Null dereference causing crashes
LOW: Null dereference with limited impact