CVE-2026-107302: msgpack5 Truncated Map32 Headers Throw An Vulnerability

HIGH
Advisory Identifier: GHSA-8f34-f56x-9xph
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CVSS 7.5
CWE-125
Published
Advisory Summary

CVE-2026-107302 is a HIGH (CVSS 7.5) truncated map32 headers throw an vulnerability (CWE-125: Out-of-bounds Read) affecting msgpack5 libraries in the npm ecosystem. The issue involves truncated map32 headers throw an unexpected error. Remediation is available by upgrading affected packages to version 6.1.0.

CVE-2026-107302 at a Glance

CVE Identifier CVE-2026-107302
GHSA Identifier GHSA-8f34-f56x-9xph
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-125: Out-of-bounds Read
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-2026-107302

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-2026-107302, 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-125: Out-of-bounds Read, where the product reads data past the end, or before the beginning, of the intended buffer. 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 A truncated `map32` header causes an out-of-bounds buffer read and throws `RangeError` instead of `IncompleteBufferError`. Applications that rely on `IncompleteBufferError` to wait for additional bytes may terminate a request, stream, or worker unexpectedly. No adjacent memory is disclosed because the buffer implementation checks bounds. ### Patches The decoder now validates the complete five-byte `map32` header before reading its length and reports truncated input as `IncompleteBufferError`. ### Workarounds Require at least five bytes before decoding a value beginning with `0xdf`, or catch `RangeError` and treat it as incomplete input only for truncated `map32` headers.

CVE-2026-107302 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-8f34-f56x-9xph
Security Fix Commit FIX COMMIT
https://github.com/mcollina/msgpack5/commit/15443a1f2aa682a6aa37f1705ac628de5b866ad1
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-2026-107302?
CVE-2026-107302 is a security vulnerability in msgpack5 involving Truncated map32 headers throw an unexpected error under CWE-125: Out-of-bounds Read.
Which msgpack5 versions are affected?
Affected versions include releases prior to 6.1.0 across affected packages: msgpack5.
What version fixes CVE-2026-107302?
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-2026-107302?
CVE-2026-107302 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-2026-107302?
CVE-2026-107302 is classified under CWE-125: Out-of-bounds Read (The product reads data past the end, or before the beginning, of the intended buffer.).
How can I check npm dependencies for CVE-2026-107302?
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-8f34-f56x-9xph",
  "modified" : "2026-10-08T17:40:10Z",
  "published" : "2026-10-08T17:40:10Z",
  "aliases" : [ "CVE-2026-107302" ],
  "summary" : "msgpack5: Truncated map32 headers throw an unexpected error",
  "details" : "### Impact\n\nA truncated `map32` header causes an out-of-bounds buffer read and throws `RangeError` instead of `IncompleteBufferError`. Applications that rely on `IncompleteBufferError` to wait for additional bytes may terminate a request, stream, or worker unexpectedly. No adjacent memory is disclosed because the buffer implementation checks bounds.\n\n### Patches\n\nThe decoder now validates the complete five-byte `map32` header before reading its length and reports truncated input as `IncompleteBufferError`.\n\n### Workarounds\n\nRequire at least five bytes before decoding a value beginning with `0xdf`, or catch `RangeError` and treat it as incomplete input only for truncated `map32` headers.",
  "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-8f34-f56x-9xph"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mcollina/msgpack5/commit/15443a1f2aa682a6aa37f1705ac628de5b866ad1"
  }, {
    "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-125" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-08T17:40:10Z",
    "nvd_published_at" : null
  }
}