CVE-2026-107297: msgpack5 Quadratic Parsing Vulnerability

MODERATE
Advisory Identifier: GHSA-gcx5-hxj7-gpqq
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CVSS 5.9
CWE-407
Published
Advisory Summary

CVE-2026-107297 is a MODERATE (CVSS 5.9) quadratic parsing vulnerability (CWE-407: Inefficient Algorithmic Complexity) affecting msgpack5 libraries in the npm ecosystem. The issue involves quadratic parsing in the streaming decoder. Remediation is available by upgrading affected packages to version 6.1.0.

CVE-2026-107297 at a Glance

CVE Identifier CVE-2026-107297
GHSA Identifier GHSA-gcx5-hxj7-gpqq
Severity MODERATE
CVSS v3.1 Base Score 5.9
CWE Classification CWE-407: Inefficient Algorithmic Complexity
Affected Product msgpack5
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.9

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

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
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-2026-107297

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-2026-107297, 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-407: Inefficient Algorithmic Complexity, where an algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached. 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 reparses an incomplete container from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack value across many small chunks, causing quadratic CPU usage and blocking the event loop. ### Patches The decoder now preserves incremental container state so completed elements are not parsed again when more input arrives. ### Workarounds Buffer each complete MessagePack value before decoding it, or limit the number of chunks accepted for a single value.

CVE-2026-107297 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-gcx5-hxj7-gpqq
Security Fix Commit FIX COMMIT
https://github.com/mcollina/msgpack5/commit/e4827641d3105e295cbbd56e9c5389978547eab4
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-2026-107297?
CVE-2026-107297 is a security vulnerability in msgpack5 involving Quadratic parsing in the streaming decoder under CWE-407: Inefficient Algorithmic Complexity.
Which msgpack5 versions are affected?
Affected versions include releases prior to 6.1.0 across affected packages: msgpack5.
What version fixes CVE-2026-107297?
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-2026-107297?
CVE-2026-107297 has a CVSS v3.1 base score of 5.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-107297?
CVE-2026-107297 is classified under CWE-407: Inefficient Algorithmic Complexity (An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.).
How can I check npm dependencies for CVE-2026-107297?
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-gcx5-hxj7-gpqq",
  "modified" : "2026-10-08T17:39:46Z",
  "published" : "2026-10-08T17:39:46Z",
  "aliases" : [ "CVE-2026-107297" ],
  "summary" : "msgpack5: Quadratic parsing in the streaming decoder",
  "details" : "### Impact\n\nThe streaming decoder reparses an incomplete container from the beginning whenever another chunk arrives. A remote peer can split one valid MessagePack value across many small chunks, causing quadratic CPU usage and blocking the event loop.\n\n### Patches\n\nThe decoder now preserves incremental container state so completed elements are not parsed again when more input arrives.\n\n### Workarounds\n\nBuffer each complete MessagePack value before decoding it, or limit the number of chunks accepted for a single value.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/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-gcx5-hxj7-gpqq"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mcollina/msgpack5/commit/e4827641d3105e295cbbd56e9c5389978547eab4"
  }, {
    "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-407" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-08T17:39:46Z",
    "nvd_published_at" : null
  }
}