The vulnerability stems from improper size validation when creating inline array segments. The patch adds critical size checks (AssertOrFailFast and min() operation) to prevent segments from exceeding INLINE_CHUNK_SIZE. The unpatched functions InitArrayAndHeadSegment and FillSegmentBuffer directly used alignedInlineElementSlots without validation, which could be larger than the inline buffer allocation due to alignment padding. This mismatch between allocated size and operational size would enable out-of-bounds writes (CWE-787), consistent with the described memory corruption vulnerability.