CVE-2026-86040 libp2p: Unbounded RPC decode + synchronous subscription processing in @libp2p/floodsub allows unauthenticated DoS
Remote attackers can cause CPU exhaustion and memory leaks in libp2p floodsub via unbounded RPC decoding, leading to node unavailability.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-86040?
CVE-2026-86040 is a high-severity denial of service vulnerability in @libp2p floodsub, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
libp2p is a JavaScript implementation of the libp2p networking stack. Prior to 11.0.26, @libp2p/floodsub accepts unauthenticated RPC frames on /floodsub/1.0.0 through PeerStreams.attachInboundStream in packages/floodsub/src/peer-streams.ts without protobuf element limits, then processRpc and processRpcSubOpt in packages/floodsub/src/floodsub.ts synchronously process the subscriptions array without a per-frame cap. A single bounded-size frame can decode into millions of empty subscription entries that block the event loop, while hundreds of thousands of unique-topic SUBSCRIBE entries allocate PeerSet objects in this.topics that are not removed after peer removal or stop. Empty entries cause CPU exhaustion but do not grow this.topics; persistent memory growth requires unique topics. The subscription path bypasses message signature validation and the message-only processing queue, allowing a remote peer to cause sustained CPU denial of service, memory exhaustion, out-of-memory termination, and node unavailability. The issue is fixed in version 11.0.26.
Which versions are affected by CVE-2026-86040?
How do I fix CVE-2026-86040?
No fix has been published for CVE-2026-86040 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-86040 being exploited?
There is no known exploitation of CVE-2026-86040 in the wild and no public exploit code.
Sources
Also known as GHSA-cvfg-hcf3-ggwv.