libp2p: CPU DoS via oversized IHAVE and IWANT control message arrays (CVE-2026-49866) | HOL Guard CVE

High · CVSS 7.5CVE-2026-49866GHSA-CWC9-CP4J-MCVV

libp2p: CPU DoS via oversized IHAVE and IWANT control message arrays

Answer in brief

CVE-2026-49866 records a High severity (CVSS 7.5) vulnerability in libp2p: CPU DoS via oversized IHAVE and IWANT control message arrays. 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 Jul 8, 2026Updated Jul 10, 2026Source checked Sep 17, 2026First seen by HOL Jul 8, 2026Material review Jul 10, 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	< 16.0.0	Not reported
@libp2p/gossipsubnpm	<16.0.0	16.0.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for libp2p/js-libp2p, @libp2p/gossipsub.
Review the reported fix. Update @libp2p/gossipsub to 16.0.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Jul 10, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jul 8, 2026

Sources and claim methodology

Upstream source description

libp2p is a JavaScript Implementation of libp2p networking stack. Prior to 16.0.0, @libp2p/gossipsub defaultDecodeRpcLimits set maxIhaveMessageIDs and maxIwantMessageIDs to Infinity, allowing oversized IHAVE and IWANT control message arrays in message/decodeRpc.ts and gossipsub.ts to synchronously iterate roughly 180,000 message IDs per 4 MB frame and block the Node.js event loop. This issue is fixed in version 16.0.0.

Quoted source text, attributed separately from HOL analysis.