Vulnerability · Published Sep 17, 2026 · Assigned by GitHub_M
CVE-2026-86038libp2p: Gossipsub StrictSign accepts attacker-signed messages as a victim RSA peer ID
High 7.5
In plain English
A high-severity insufficient verification of data authenticity in js-libp2p from libp2p. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | @libp2p/gossipsub | 16.0.5 | GHSA-c3gv-825q-fvmp |
Affected products (as reported)
Weakness: CWE-345, CWE-347 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
References
- https://github.com/libp2p/js-libp2p/security/advisories/GHSA-c3gv-825q-fvmp x_refsource_CONFIRM
- https://github.com/libp2p/js-libp2p/pull/3569 x_refsource_MISC
- https://github.com/libp2p/js-libp2p/commit/cec2b1f349d130065e561349a0336a239528267f x_refsource_MISC
- https://github.com/libp2p/js-libp2p/releases/tag/gossipsub-v16.0.5 x_refsource_MISC