NRDAX-T0349 - Unseeded Hash Collision DoS

Compute amplification · P2P and gossip · no bound · active · first seen 2026-07-11

provenance: Reproduced in NullRabbit's attack-reproduction pipeline

mechanism

QUIC SCID hash-collision DoS (CVE-2025-47200): a flood of QUIC v1 Initial packets whose 8-byte Source Connection IDs are crafted to COLLIDE in the server's connection-ID hash table. The server keys active connections on the peer SCID; a weak non-seeded hash (NCC names FNV, xxHash, and `hash = hash*31 + char`) lets the attacker hold a constant 5-byte SCID prefix (5c1dc011de) and vary a 3-byte counter suffix, keeping only suffixes whose full-SCID hash lands in one target bucket - so every DISTINCT SCID collides. Worst-case O(n) bucket walks (amortised O(n^2)) burn server CPU: NCC measured ~300x slowdown from 10k parallel colliding connections. Only SipHash (keyed) mitigates. PUBLIC-CVE replication of the NCC Group / Fox-IT advisory; new corpus wire family = algorithmic-complexity / hash-DoS.

live exposure

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

instances (1)

chain	primitive	fidelity	origin	reproducer (bundle)	source
quic	quic_scid_collision_hash_dos	lab	reverse-engineered-cve	quic_scid_collision_hash_dos	CVE-2025-47200 ↗

related (Compute amplification)

NRDAX-T0006 - Async Runtime Blocking VM Execution active NRDAX-T0076 - Expensive Debug RPC Compute Amplification active NRDAX-T0088 - GetData Request Flood active NRDAX-T0100 - Handshake Crypto CPU Burn active NRDAX-T0139 - Legacy Sighash Quadratic CPU Blowup active NRDAX-T0143 - Malformed Field Gossip Before Validation active NRDAX-T0148 - Malformed KZG Proof Mismatch DoS active NRDAX-T0166 - Move Verifier Fixpoint CPU Exhaustion active

cite

https://nrdax.com/techniques/NRDAX-T0349

plain

NRDAX Registry. Technique NRDAX-T0349.

bibtex

@misc{nrdax_NRDAX_T0349,
  title = {Unseeded Hash Collision DoS (NRDAX-T0349)},
  howpublished = {NRDAX Registry},
  url = {https://nrdax.com/techniques/NRDAX-T0349},
}

json (csl)

{
  "id": "nrdax-NRDAX-T0349",
  "type": "dataset",
  "title": "Unseeded Hash Collision DoS (NRDAX-T0349)",
  "URL": "https://nrdax.com/techniques/NRDAX-T0349",
  "publisher": "NRDAX Registry"
}

badge

[![NRDAX-T0349 in the NRDAX registry](https://nrdax.com/badge/NRDAX-T0349.svg)](https://nrdax.com/techniques/NRDAX-T0349-unseeded-hash-collision-dos)

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-T0349

Cite it (BibTeX)

nrdax cite NRDAX-T0349 --format bibtex

CLI guide → GitHub ↗