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Application & OT Security · Intermediate

Null Pointer Dereference

Accessing memory through a pointer whose value is null, typically causing a crash and denial of service.

Definition

Usually caused by unchecked return values or failed allocations. In user-space it is mainly an availability issue; in some kernel contexts it has enabled privilege escalation. Prevent with null checks, optional types and static analysis. Tracked as CWE-476.

Example

A parser does not check whether a lookup returned null and crashes on malformed input.

Exam tip

Mostly a DoS weakness; checking return values prevents it.

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