AIKIDO-2026-826894

TL;DR

The reflective DynamicMessage decoder in buffa-descriptor materializes the elements of repeated fields and map entries without bounding the memory they consume. An attacker who supplies a small protobuf payload containing many empty repeated-message, string, bytes, or map elements can force the decoder to allocate far more memory than the input size, because each element expands to its full in-memory footprint on decode. Before the fix no decode option bounded this in-decode expansion, so untrusted input could exhaust process memory. The fix adds a per-decode element-memory budget (DecodeOptions::with_element_memory_limit, default 32 MiB) that charges each materialized element and rejects over-budget input with DecodeError::ElementMemoryLimitExceeded.