CVE-2026-49866

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.6% (48th percentile of EPSS-scored CVEs). 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
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 7.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
49
EG Risk 49/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation1% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.6%
EPSS %ILE
48th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

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-v16.0.0
github_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/773dd80ded24dbd6b19e675c89fd2f3b45f2d899
github_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/3520
githubMentions a patch (unverified)🟡 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-mcvv

Vendor 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)
PackageVulnerable rangeFix by version rangeDependents
@libp2p/gossipsub—
  • every version up to 16.0.0: fixed in 16.0.0
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 6× in last 7d / 27× 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.

Showing the most recent 100 of 126 total refreshes for this CVE.

  1. 2026-10-10 20:00 UTCEPSS rescore
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  3. 2026-10-08 17:12 UTCEPSS rescore
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  1. 2026-09-12 03:30 UTCEG score recompute
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  24. 2026-08-24 22:12 UTCEG score recompute
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  74. 2026-07-28 17:15 UTCEG score recompute
  75. 2026-07-28 15:37 UTCEPSS rescore

Related CVEs(same product + same CWE)

Same product

2 shown

npm:@libp2p/gossipsub

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 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 0.6% probability of exploitation in the next 30 days (48th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-49866?
CVE-2026-49866 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-49866?
A fix for CVE-2026-49866 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-49866 are linked in the Vendor Advisories panel on this page.

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