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CVE-2026-107300

HIGH 7.5

Published 2026-10-08 · Last modified 2026-10-08

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, the streaming decoder recursively invokes itself for each complete MessagePack value remaining in a chunk. A remote peer can send one chunk containing many small valid values, causing recursion proportional to the value count, exhausting the JavaScript call stack, and interrupting the process or stream. This issue is fixed in version 6.1.0.

ELEVATED IMPACT

Severe if exploited (CVSS 7.5), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

0.4%chance of exploitation in 30 days · 37th percentile

○ In CISA KEV ○ Catalogued PoC

Impact if exploited

7.5CVSS 3.1 · HIGH

  • ConfidentialityNone
  • IntegrityNone
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

Search for new PoCs

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Tracked sources are checked daily for recent CVEs, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Data snapshot:

Affected

Vendors Mcollina

Products Msgpack5

Weakness (CWE)

  • CWE-674: : Uncontrolled Recursion

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References and research data (JSON)

Packages and version ranges

Each advisory describes its own package and affected ranges. A boundary applies to that range; it is not a universal upgrade recommendation.

  • msgpack5 npm

    pkg:npm/msgpack5

    SEMVER range
    • All earlier versions (introduced 0)
    • Fixed boundary (excluded): 6.1.0
    Additional upstream package constraints
    {
  "database": {
    "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-5x5g-h9x8-2fh9/GHSA-5x5g-h9x8-2fh9.json"
  }
}
    GitHub Advisory Database · GHSA-5x5g-h9x8-2fh9 · Updated 2026-10-08T18:00:08.893076738Z

All CVSS metrics

  • HIGH 7.5 v3.1 · CNA Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  • HIGH 7.5 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Advisories

Technical & other

Sources: NVD · CVE.org · EPSS