libp2p: Gossipsub StrictSign accepts attacker-signed messages as a victim RSA peer ID (CVE-2026-86038) | HOL Guard CVE

High · CVSS 7.5CVE-2026-86038GHSA-C3GV-825Q-FVMP

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

Answer in brief

CVE-2026-86038 records a High severity (CVSS 7.5) vulnerability in libp2p: Gossipsub StrictSign accepts attacker-signed messages as a victim RSA peer ID. The current sources do not mark it as known exploited. The current feed maps libp2p/js-libp2p (generic), @libp2p/gossipsub (npm). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 17, 2026Updated Sep 17, 2026Source checked Sep 17, 2026First seen by HOL Sep 17, 2026Material review Sep 17, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps libp2p/js-libp2p (generic), @libp2p/gossipsub (npm). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
libp2p/js-libp2pgeneric	>= 15.0.0, < 16.0.5	Not reported
@libp2p/gossipsubnpm	>=15.0.0,<16.0.5	16.0.5

Recommended response

Check inventory. Check lockfiles and deployed manifests for libp2p/js-libp2p, @libp2p/gossipsub.
Review the reported fix. Update @libp2p/gossipsub to 16.0.5 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 17, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 17, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 17, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.