How can developers prevent use of an out-of-range pointer offset?

What makes an out-of-range pointer offset dangerous?

An out-of-range pointer offset becomes dangerous when pointer arithmetic no longer points within the original object or permitted array span. At that point, the program may read or write unrelated memory, corrupt state, or trigger undefined behaviour. The practical problem is not just a crash, it is losing the guarantee that the pointer still refers to the intended object.

In C and C++ style memory models, safe arithmetic depends on object boundaries, not just on whether the resulting address looks plausible. A value can be numerically valid and still be semantically invalid if it crosses the end of the allocation, wraps around, or is computed from a stale base pointer.

How do developers keep pointer arithmetic inside valid bounds?

The safest pattern is to treat the offset as untrusted input until it has been checked against the size of the object or array. That means validating the offset before addition, using unsigned or range-checked calculations carefully, and rejecting any value that would move the pointer before the start or beyond the end of the allocation. Index-based access with explicit bounds checks is usually easier to reason about than manual pointer stepping.

When the offset comes from external data, convert and validate it early. If the code accepts signed values, negative offsets need explicit rejection before any cast or addition happens. If the code accepts large sizes, guard against overflow in the intermediate arithmetic so the check itself cannot be bypassed by wraparound.

Where possible, prefer language and library facilities that keep the object and bounds together, such as spans, slices, iterators with bounds awareness, or helper functions that take length alongside the base pointer. Those abstractions reduce the chance that a pointer escapes its intended range during refactoring.

Which testing and tooling help catch bad offsets before release?

Static review should focus on the exact places where a base pointer is adjusted by a computed index, length, or delta. Those sites often look harmless in isolation but become unsafe when assumptions change, especially after type conversions or when a length is reused from a different buffer.

Dynamic testing should include fuzzing and sanitised builds because they expose edge cases that ordinary tests miss, especially wraparound, off-by-one errors, and offset values that land just outside a buffer. Sanitizers can turn an invisible memory bug into a reproducible failure, which is far more useful than trying to infer the problem from downstream symptoms.

Code review should also check whether the same bounds rule is applied consistently across all call sites. A single unchecked helper that is reused widely can undermine otherwise careful code.

Risk and Threat Considerations

Out-of-range pointer offsets are a memory safety risk because they can turn a small arithmetic mistake into memory corruption, data disclosure, or an exploitable write primitive. In security-sensitive code, the main concern is not only correctness, but whether the bad pointer can be influenced by attacker-controlled input or by malformed file, network, or protocol data.

Failure mechanism: The offset calculation escapes the intended allocation through overflow, underflow, sign conversion, or a stale size assumption, and the resulting pointer is then dereferenced or used in a copy operation.

Impact: The program may crash, read sensitive adjacent memory, overwrite control data, or create a path to arbitrary code execution depending on the surrounding memory layout and subsequent use.

Practitioner Guidance

What to verify: Confirm that every pointer adjustment is preceded by a bounds check that uses the same base object and the same length that will govern the dereference. Do not trust a check performed on a different representation, such as a pre-conversion integer or a related buffer length.

Common mistake: Developers often validate the final pointer after arithmetic instead of validating the offset before arithmetic. That is risky when the arithmetic can wrap, because the check may already be operating on a corrupted value.

Practitioner takeaway: Treat pointer offsets as a boundary problem first and a coding style problem second, because the safest fix is the one that makes it impossible for the arithmetic to outgrow the object in the first place.

Related resources from NHI Mgmt Group

• Guide: CWE Top 25 Guide
• Is CVE-2023-33106 (Qualcomm Multiple Chipsets Use of Out-of-Range Pointer Offset) being exploited in the wild?
• How do you patch or mitigate CVE-2023-33106 (Qualcomm Multiple Chipsets Use of Out-of-Range Pointer Offset)?
• What causes Use of Out-of-range Pointer Offset?
• CVE-2023-33106 (Qualcomm Multiple Chipsets Use of Out-of-Range Pointer Offset)