NRDAX-T0064 - Endpoint Concurrency Cap Exhaustion

Connection exhaustion · RPC and public API · no bound · active · first seen 2026-07-04

provenance: Reproduced in NullRabbit's attack-reproduction pipeline

mechanism

cosmos-sdk server/grpc/server.go grpc.NewServer w/o grpc.MaxConcurrentStreams -> grpc-go default effectively unbounded + no SETTINGS_MAX_CONCURRENT_STREAMS signalled; attacker holds many HTTP/2 streams on one conn pinning per-stream state (~7KB) -> ~7GB single-source RSS pin (measured gaiad loopback). Sei fork sets MaxConcurrentStreams(100). COSMOS_SDK_GRPC_STREAM_FLOOD / C11.

live exposure

No exposure data. Slashr ↗ has no risk signal mapped to this technique yet — absence of data is not absence of exposure.

research

In-depth write-ups of this attack on nullrabbit.ai.

rusty-kaspa gRPC pre-auth HTTP/2 stream flood causing inbound-peering exhaustion and eviction ↗

instances (5)

chain	primitive	fidelity	origin	reproducer (bundle)	source
cosmos	cosmos_grpc_stream_flood	lab	NullRabbit Labs	cosmos_grpc_stream_flood	-
http2	http2_settings_ack_stream_cap_bypass	lab	reverse-engineered-cve	http2_settings_ack_stream_cap_bypass	-
ic	ic_xnet_concurrency_cap	lab	NullRabbit Labs	ic_xnet_concurrency_cap	github.com ↗
iota	iota_grpc_stream_cap_dos	lab	NullRabbit Labs	iota_grpc_stream_cap_dos	-
kaspa	kaspa_grpc_h2_preauth_stream_flood	lab	NullRabbit Labs	kaspa_grpc_h2_preauth_stream_flood	-

related (Connection exhaustion)

NRDAX-T0041 - Cross-Chain Peer Pool Pollution active NRDAX-T0099 - Half-Open Handshake Slowloris active NRDAX-T0214 - Protocol Message Flood Unbounded Goroutine active NRDAX-T0225 - QUIC Control Frame Flood active NRDAX-T0246 - Rate-Limit Key Confusion active NRDAX-T0261 - RPC Request Flood active NRDAX-T0291 - Subscription Permit Exhaustion active NRDAX-T0320 - Unbounded Connection Flood active

cite

https://nrdax.com/techniques/NRDAX-T0064

plain

NRDAX Registry. Technique NRDAX-T0064.

bibtex

@misc{nrdax_NRDAX_T0064,
  title = {Endpoint Concurrency Cap Exhaustion (NRDAX-T0064)},
  howpublished = {NRDAX Registry},
  url = {https://nrdax.com/techniques/NRDAX-T0064},
}

json (csl)

{
  "id": "nrdax-NRDAX-T0064",
  "type": "dataset",
  "title": "Endpoint Concurrency Cap Exhaustion (NRDAX-T0064)",
  "URL": "https://nrdax.com/techniques/NRDAX-T0064",
  "publisher": "NRDAX Registry"
}

badge

[![NRDAX-T0064 in the NRDAX registry](https://nrdax.com/badge/NRDAX-T0064.svg)](https://nrdax.com/techniques/NRDAX-T0064-endpoint-concurrency-cap-exhaustion)

use from the CLI

Retrieve or cite this technique from a script or the terminal with the NRDAX Python library & CLI.

Retrieve this technique

nrdax get NRDAX-T0064

Cite it (BibTeX)

nrdax cite NRDAX-T0064 --format bibtex

CLI guide → GitHub ↗