msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder treats the reserved MessagePack byte 0xc1 as incomplete input instead of invalid input. When 0xc1 begins a stream, subsequent data remains buffered while the decoder waits for bytes that cannot make the value valid, allowing a remote peer to exhaust memory. This issue is fixed in version 6.1.0.
CVE-2026-107299
MEDIUMPre-NVD 5.95.9Trending — 3 sources updated this week
EchelonGraph scoreLOW confidence
This medium-severity CVE scores 5.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). 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: secondary
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 5.9Exploit: None knownExposed services: Not assessed
A fix is available — apply it.
- CVSS v3
- 5.9
- EG Score
- 5.9MEDIUMlow confidence
- EG Risk
- 27EG Risk 27/100CISA 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 computedSeverity59% × 45%Exploitation0% × 40%Automatability0% × 15%CISA SSVC: Track at every mission impact level.Action: A fix is available. Apply it within your standard update timelines. - EPSS PROB
- 0.4%
- EPSS %ILE
- 30th
- KEV
- Not listed
CISA SSVCTrack at every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (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
October 8, 2026
Last Modified
October 9, 2026
Advisory Details (3)
Auto-updated Oct 8, 2026Patch available. Sources: github_release, github, github_commit.
githubMentions a patch (unverified)
Reserved byte can cause unbounded stream buffering · Advisory · mcollina/msgpack5 · GitHub
https://github.com/mcollina/msgpack5/security/advisories/GHSA-26wq-p25c-j6fvgithub_release Patch Available
v6.1.0
Patch available: mcollina/msgpack5 v6.1.0
https://github.com/mcollina/msgpack5/releases/tag/v6.1.0github_commit Patch Available
commit 85da345bf1ac (mcollina/msgpack5)
Patch available: mcollina/msgpack5 v6.1.0 (contains commit 85da345bf1ac)
https://github.com/mcollina/msgpack5/commit/85da345bf1acc18ca441741e5cf4aa0ed0d69314Vendor Advisories for CVE-2026-107299(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 | Fix by version range | Dependents |
|---|---|---|---|
| msgpack5 | — |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 6× in last 7d / 6× 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.
- 2026-10-09 20:06 UTCEPSS rescore
- 2026-10-09 16:35 UTCEG score recompute
- 2026-10-09 15:26 UTCEG score recompute
- 2026-10-08 17:25 UTCEG score recompute
- 2026-10-08 17:15 UTCEG score recompute
- 2026-10-08 17:14 UTCMITRE cvelistV5first tracked
Related CVEs(same product + same CWE)
Same product
7 shownnpm:msgpack5
Frequently asked(5)
What is CVE-2026-107299?
CVE-2026-107299 is a medium vulnerability published on October 8, 2026. msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder treats the reserved MessagePack byte 0xc1 as incomplete input instead of invalid input. When 0xc1 begins a stream, subsequent data remains buffered while the decoder waits for bytes that…
When was CVE-2026-107299 disclosed?
CVE-2026-107299 was first published on October 8, 2026, with the most recent update on October 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-107299 actively exploited?
CVE-2026-107299 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (30th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-107299?
CVE-2026-107299 has a CVSS base score of 5.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-107299?
A fix for CVE-2026-107299 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-107299 are linked in the Vendor Advisories panel on this page.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-107299
Is Your Infrastructure Affected by CVE-2026-107299?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.