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TI-2026-69606 Aliases CVE-2026-107301GHSA-8hq7-ggx2-cc6m

Prototype pollution in msgpack5 with partial options

Priority LOW 29CWE-1321Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
None · High · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.

Summary

msgpack5 before 6.1.0 disables its default protoAction error protection when constructed with an empty or partial options object. An attacker who can supply msgpack data can use a decoded map with a __proto__ key to replace the prototype of the decoded object, which may change inherited properties or downstream behavior (CWE-1321). Object.prototype is not modified globally.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

msgpack5 is a msgpack v5 implementation for node.js and the browser. Prior to 6.1.0, constructing msgpack5 with an empty or partial options object disables the default protoAction: 'error' protection. A decoded map containing a __proto__ key can then replace the decoded object's prototype, potentially changing inherited properties or downstream behavior, although Object.prototype is not modified globally. This issue is fixed in version 6.1.0.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00366 30th percentileScored 2026-11-07
Fix Fixed msgpack5 (mcollina): 6.1.0msgpack5 (npm): 6.1.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
mcollinamsgpack5before 6.1.06.1.0Patch availableCNA
—msgpack5 (npm)before 6.1.06.1.0Patch availableGHSA-8hq7-ggx2-cc6m
  • msgpack5 Vendormcollina Affected before 6.1.0 Fixed in 6.1.0 Patch available CNA
  • msgpack5 (npm) Vendor— Affected before 6.1.0 Fixed in 6.1.0 Patch available GHSA-8hq7-ggx2-cc6m

Remediation

Update the npm package msgpack5 to version 6.1.0, which fixes this issue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

  • Fix · CNA msgpack5 (mcollina) Fixed in 6.1.0
  • Fix · GHSA-8hq7-ggx2-cc6m msgpack5 (npm) Fixed in 6.1.0 Advisory →

Timeline

  1. 2026-10-08 Threatist record created from CVE-2026-107301
  2. 2026-10-08 Alias added: GHSA-8hq7-ggx2-cc6m
  3. 2026-10-10 Priority changed: MEDIUM → LOW
  4. 2026-10-14 CISA SSVC decision points changed

References

Other 4

  • TI-2026-76780 Command injection in mcollina mcp-ripgrep Advanced Search Tool CVSS 4.0MEDIUM 4.8
  • TI-2026-69605 Truncated map32 headers throw RangeError in msgpack5 decoder CVSS 3.1HIGH 7.5
  • TI-2026-69603 msgpack5 streaming decoder recursion can exhaust the call stack CVSS 3.1HIGH 7.5
  • TI-2026-69599 Deeply nested input exhausts the stack in msgpack5 decoder CVSS 3.1MEDIUM 5.3
  • TI-2026-69609 Quadratic parsing in msgpack5 streaming decoder blocks the event loop CVSS 3.1MEDIUM 5.9
  • TI-2026-69600 Reserved byte in msgpack5 causes unbounded stream buffering CVSS 3.1MEDIUM 5.9
See all 7 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences