CVE-2026-107300: msgpack5 Many Buffered Values Can Exhaust Vulnerability

HIGH
Advisory Identifier: GHSA-5x5g-h9x8-2fh9
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CVSS 7.5
CWE-674
Published
Advisory Summary

CVE-2026-107300 is a HIGH (CVSS 7.5) many buffered values can exhaust vulnerability (CWE-674: Uncontrolled Recursion) affecting msgpack5 libraries in the npm ecosystem. The issue involves many buffered values can exhaust the streaming decoder stack. Remediation is available by upgrading affected packages to version 6.1.0.

CVE-2026-107300 at a Glance

CVE Identifier CVE-2026-107300
GHSA Identifier GHSA-5x5g-h9x8-2fh9
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-674: Uncontrolled Recursion
Affected Product msgpack5
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-107300

To remediate this vulnerability, upgrade all affected msgpack5 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

msgpack5 fixed: 6.1.0 
npm install msgpack5@6.1.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls msgpack5

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-107300, inspect your project dependencies using npm:

npm ls msgpack5

Analyze the terminal output to locate any version of msgpack5 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.1.0), your application is affected.

Note: The npm ls msgpack5 command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-674: Uncontrolled Recursion, where the product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack. In msgpack5, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact The streaming decoder recursively invokes itself for every complete value remaining in a chunk. A single chunk containing many small valid MessagePack values can exhaust the JavaScript call stack and interrupt the process or stream. ### Patches The streaming decoder now drains concatenated values iteratively with constant call-stack depth. ### Workarounds Limit the number of MessagePack values accepted in one chunk, or split large batches before passing them to the decoder stream.

CVE-2026-107300 Affected msgpack5 Versions

1 component(s)
Fixed Versions:
6.1.0
Product / Package Ecosystem Affected Versions Fixed Version
msgpack5
npm/msgpack5
npm
< 6.1.0
6.1.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/mcollina/msgpack5/security/advisories/GHSA-5x5g-h9x8-2fh9
Security Fix Commit FIX COMMIT
https://github.com/mcollina/msgpack5/commit/77fbef144d05def5d16fc22c37caa64c0a7efeba
msgpack5 Source Repository REPOSITORY
https://github.com/mcollina/msgpack5
msgpack5 Release RELEASE
https://github.com/mcollina/msgpack5/releases/tag/v6.1.0

Frequently Asked Questions

What is CVE-2026-107300?
CVE-2026-107300 is a security vulnerability in msgpack5 involving Many buffered values can exhaust the streaming decoder stack under CWE-674: Uncontrolled Recursion.
Which msgpack5 versions are affected?
Affected versions include releases prior to 6.1.0 across affected packages: msgpack5.
What version fixes CVE-2026-107300?
Upgrading to 6.1.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is msgpack5 affected?
Yes, msgpack5 is affected in releases prior to 6.1.0. Upgrade your dependency to 6.1.0 or later.
What is the CVSS score of CVE-2026-107300?
CVE-2026-107300 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-107300?
CVE-2026-107300 is classified under CWE-674: Uncontrolled Recursion (The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.).
How can I check npm dependencies for CVE-2026-107300?
Run the dependency tree command: 'npm ls msgpack5'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-5x5g-h9x8-2fh9",
  "modified" : "2026-10-08T17:40:06Z",
  "published" : "2026-10-08T17:40:06Z",
  "aliases" : [ "CVE-2026-107300" ],
  "summary" : "msgpack5: Many buffered values can exhaust the streaming decoder stack",
  "details" : "### Impact\n\nThe streaming decoder recursively invokes itself for every complete value remaining in a chunk. A single chunk containing many small valid MessagePack values can exhaust the JavaScript call stack and interrupt the process or stream.\n\n### Patches\n\nThe streaming decoder now drains concatenated values iteratively with constant call-stack depth.\n\n### Workarounds\n\nLimit the number of MessagePack values accepted in one chunk, or split large batches before passing them to the decoder stream.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "msgpack5"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.1.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/mcollina/msgpack5/security/advisories/GHSA-5x5g-h9x8-2fh9"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mcollina/msgpack5/commit/77fbef144d05def5d16fc22c37caa64c0a7efeba"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mcollina/msgpack5"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mcollina/msgpack5/releases/tag/v6.1.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-674" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-08T17:40:06Z",
    "nvd_published_at" : null
  }
}