A Product Change Notice is a vendor document that announces a change to a hardware part, component, process, or specification that may affect compatibility. PCNs are common in supply-chain management because they tell customers when a chip revision, memory part, or board layout has changed and whether existing systems still work as expected.
In cyber security, PCNs matter because hardware changes can alter boot behavior, trust assumptions, and patching plans. A PCN may reveal that a device now needs a newer firmware version, that a replacement part is no longer qualified, or that a refurbished system may behave differently from an original build. Defenders use PCNs to track approved components, validate firmware updates, and detect unexpected substitutions. Attackers can benefit when organizations ignore PCNs, since unreviewed hardware swaps can introduce incompatibilities, weaken integrity checks, or hide provenance problems in the supply chain.