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CVE-2026-86038 high CVSS 7.5

Vulnerability in @libp2p/gossipsub (CVE-2026-86038)

Summary

Vulnerability in @libp2p/gossipsub (CVE-2026-86038). Data can be tampered with by attackers. Exploitable via StrictSign. Mitigation: upgrade to 16.0.5 or later.

Original description

The description as published by the source.

Summary

@libp2p/gossipsub StrictSign validation does not bind a supplied message public key to the claimed from peer ID when from is an RSA-style peer ID that does not inline its public key. An attacker can set from to a victim RSA peer ID, sign the message with the attacker's own private key, include the attacker's public key in msg.key, and have the message accepted as a valid signed message from the victim.

Details

The vulnerable code is in packages/gossipsub/src/utils/buildRawMessage.ts inside validateToRawMessage.

When msg.key is present:

publicKey = publicKeyFromProtobuf(msg.key)
if (fromPeerId.publicKey !== undefined && !publicKey.equals(fromPeerId.publicKey)) {
  return { valid: false, error: ValidateError.InvalidPeerId }
}

For RSA peer IDs parsed from the wire from multihash, fromPeerId.publicKey is undefined because the RSA public key is not inlined in the peer ID. This means the key-to-from comparison is skipped. The code then verifies the signature with the attacker-supplied msg.key and returns a signed message whose from is the victim RSA peer ID.

The missing invariant is:

peerIdFromPublicKey(publicKey).equals(fromPeerId)

This check must be performed whenever a public key is supplied, including keyless peer ID representations such as RSA peer IDs.

StrictSign is the default gossipsub signature policy in packages/gossipsub/src/gossipsub.ts:

this.globalSignaturePolicy = opts.globalSignaturePo…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-86038 has been found in @libp2p/gossipsub.
Attackers can target a specific entry point like StrictSign over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade @libp2p/gossipsub to 16.0.5 or later.
If unsure, ask your IT team or search "@libp2p/gossipsub CVE-2026-86038" on the vendor's site.

CVE-2026-86038 (@libp2p/gossipsub) — CWE-345 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: StrictSign / from / msg.key / validateToRawMessage
Patched: 16.0.5 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-345) exists in @libp2p/gossipsub. Attackers reach the vulnerable code path via StrictSign without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of @libp2p/gossipsub. Attack surface: StrictSign / from / msg.key / validateToRawMessage.

🔥 Severity

Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 16.0.5.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r '@libp2p/gossipsub' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r '@libp2p/gossipsub' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で @libp2p/gossipsub を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade @libp2p/gossipsub to 16.0.5

    ステージング環境で 16.0.5 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm @libp2p/gossipsub
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"16.0.5"}]}]

References

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