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.
CVE-2026-49866
HIGHPre-NVD 7.57.5—Trending — 3 sources updated this week
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 64% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(medium)
- EPSS
- 35.9%
- KEV
- Not listed
Published
July 8, 2026
Last Modified
July 10, 2026
Advisory Details (4)
Auto-updated Jul 8, 2026🔬 Proof of concept available. Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available
gossipsub: v16.0.0
Patch available: libp2p/js-libp2p gossipsub-v16.0.0
https://github.com/libp2p/js-libp2p/releases/tag/gossipsub-v16.0.0github_commit Patch Available
commit 773dd80ded24 (libp2p/js-libp2p)
Patch available: libp2p/js-libp2p transport-interop-libp2p-main-v1.0.32 (contains commit 773dd80ded24)
https://github.com/libp2p/js-libp2p/commit/773dd80ded24dbd6b19e675c89fd2f3b45f2d899github_pr Patch Available
fix(gossipsub)!: apply decodeRpcLimits to control messages
Patch available: libp2p/js-libp2p transport-interop-libp2p-main-v1.0.32 (PR #3520 merged 2026-05-26)
https://github.com/libp2p/js-libp2p/pull/3520github Patch Available🟡 PoC Available
CPU DoS via oversized IHAVE and IWANT control message arrays · Advisory · libp2p/js-libp2p · GitHub
https://github.com/libp2p/js-libp2p/security/advisories/GHSA-cwc9-cp4j-mcvvVendor Advisories for CVE-2026-49866(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
npm(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| @libp2p/gossipsub | — | 16.0.0 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 12× in last 7d / 12× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-12 12:58 UTCEG score recompute
- 2026-07-12 05:46 UTCEPSS rescore
- 2026-07-12 00:26 UTCEG score recompute
- 2026-07-11 11:54 UTCEG score recompute
- 2026-07-11 08:27 UTCEPSS rescore
- 2026-07-10 23:22 UTCEG score recompute
- 2026-07-10 10:50 UTCEG score recompute
- 2026-07-09 22:17 UTCEG score recompute
- 2026-07-09 19:10 UTCEPSS rescore
- 2026-07-09 09:45 UTCEG score recompute
- 2026-07-08 21:12 UTCEG score recompute
- 2026-07-08 21:10 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-49866?
CVE-2026-49866 is a high vulnerability published on July 8, 2026. 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…
When was CVE-2026-49866 disclosed?
CVE-2026-49866 was first published in the National Vulnerability Database on July 8, 2026, with the most recent update on July 10, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-49866 actively exploited?
CVE-2026-49866 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 35.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-49866?
CVE-2026-49866 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-49866?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-49866, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-49866
Is Your Infrastructure Affected by CVE-2026-49866?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.