What’s Vulnerable › Vulnerabilities

CVE-2026-86038: libp2p: Gossipsub StrictSign accepts attacker-signed messages as a victim RSA peer ID

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-17 · updated 2026-09-30
• Weakness: CWE-345

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 products

• libp2p js-libp2p: from 15.0.0, < 16.0.5

References

• https://github.com/libp2p/js-libp2p/commit/cec2b1f349d130065e561349a0336a239528267f
• https://github.com/libp2p/js-libp2p/pull/3569
• https://github.com/libp2p/js-libp2p/releases/tag/gossipsub-v16.0.5
• https://github.com/libp2p/js-libp2p/security/advisories/GHSA-c3gv-825q-fvmp
• https://github.com/libp2p/js-libp2p/security/advisories/GHSA-c3gv-825q-fvmp

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