Advisories for Golang/Github.com/Iskorotkov/Avro/V2 package

Several Avro decoder paths read attacker-controlled 64-bit values from the wire format and either narrowed them to platform-sized int before bounds-checking, or summed them with overflow-prone signed-int arithmetic. On 32-bit targets (GOARCH=386, arm, mips, wasm, etc.), the truncation paths can silently bypass byte-slice limits, select the wrong union branch, or hit the OCF negative-make panic via wrap. Three sub-issues are not 32-bit-specific: cumulative-size arithmetic overflow in arrayDecoder.Decode / mapDecoder.Decode / …

The Avro map decoder accepted attacker-controlled block-element counts from the wire format and grew the destination map without enforcing an upper bound. The slice decoder already had Config.MaxSliceAllocSize for the equivalent attack against arrays; the map decoder had no analogous limit, so a producer could declare an arbitrarily large map (in one block, or chunked across many sub-limit blocks) and exhaust process memory until the OOM killer fired. The fix …

The Avro array and map decoders looped over an attacker-controlled block-count value without checking the underlying reader's error state inside the loop body. Reader.ReadBlockHeader returns the count as a Go int, which is 64-bit on amd64 / arm64 targets — so a producer can declare a block of up to math.MaxInt64 (~9.2 × 10¹⁸) elements followed by EOF (or any truncated payload), and the decoder will attempt that many no-op …