CVE-2026-44697

## Summary A remote, unauthenticated denial-of-service vulnerability in `Batch.Decompress` (`data/batch/batch.go`) allows any peer that participates in a topic served by `MultiDataInterceptor` to allocate multi-gigabyte heaps on the receiving node from a sub-50 KiB gossip payload. A single packet is sufficient to OOM-kill a validator with conventional memory provisioning. Fleet-wide application affects chain liveness. The vulnerability was identified during an internal security review of `core/process/interceptors/multiDataInterceptor.go` at commit `405d01b0abbf0d3e73b4a990bd7394a01f200dc2`. It is distinct from, and substantially more severe than, the throttler-slot-leak vulnerability disclosed in `GHSA-74m6-4hjp-7226`. Both reports cover adjacent code in the same call path; the patches must land together in one release (rc2 superseding rc1). Two additional, lower-severity hardening issues affecting the same code path are documented in this report and remediated by the same patch. They are not independently exploitable under the default deployed anti-flood configuration and are not requested as separate CVEs. ## Description `MultiDataInterceptor.ProcessReceivedMessage` (`core/process/interceptors/multiDataInterceptor.go:79`) handles every gossip message received on the topics the interceptor is registered for. At lines 95–102 it conditionally decompresses the payload via `Batch.Decompress`: ```go if b.IsCompressed { err = b.Decompress(mdi.marshalizer) if err != nil { ... return err } } ``` `Batch.Decompress` (`data/batch/batch.go:109`) delegates the gzip step to `decompressGzip` (`data/batch/batch.go:35-53`), which performs an unbounded `io.ReadAll` on the gzip reader: ```go func decompressGzip(data []byte) ([]byte, error) { rdata := bytes.NewReader(data) reader, err := gzip.NewReader(rdata) if err != nil { return nil, err } result, err := io.ReadAll(reader) // no LimitReader, no DataSize check ... } ``` After the gzip step suc