CVE-2026-86038 libp2p: Gossipsub StrictSign accepts attacker-signed messages as a victim RSA peer ID
Attackers can forge message origins in libp2p Gossipsub by bypassing signature validation, leading to false attribution and potential abuse of trust mechanisms.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-86038?
CVE-2026-86038 is a high-severity authentication bypass vulnerability in js-libp2p, 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. From 15.0.0 until 16.0.5, @libp2p/gossipsub uses the default StrictSign policy in packages/gossipsub/src/utils/buildRawMessage.ts, where validateToRawMessage verifies a signature with attacker-controlled msg.key but skips binding that key to msg.from when the claimed author is an RSA peer ID that does not inline a public key. An unauthenticated attacker can place a victim RSA peer ID in msg.from, sign the message with the attacker's private key, and supply the attacker's public key in msg.key, causing the message to be accepted and propagated as authored by the victim. Applications that trust message.from for validators, authorization, accounting, moderation, reputation, or audit logging can process attacker-controlled data under false origin attribution. The issue is fixed in version 16.0.5.
Which versions are affected by CVE-2026-86038?
2 open source packages ship an affected version, including @libp2p/gossipsub.
| Package | Affected | Fixed in |
|---|---|---|
@libp2p/gossipsub npm | From 15.0.0 | 16.0.5 |
@libp2p/gossipsub npm | From 15.0.0 | 16.0.5 |
How do I fix CVE-2026-86038?
Upgrade @libp2p/gossipsub to 16.0.5 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-86038 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-86038 exists.
Sources
Also known as GHSA-c3gv-825q-fvmp.