CVE-2026-44291: Protobufjs Code Generation Gadget After Prototype Vulnerability

HIGH
Advisory Identifier: GHSA-75px-5xx7-5xc7
Share
CVSS 8.1
CWE-1321 CWE-94
Published
Advisory Summary

CVE-2026-44291 is a HIGH (CVSS 8.1) code generation gadget after prototype vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Protobufjs libraries in the npm ecosystem. The issue involves code generation gadget after prototype pollution. Remediation is available by upgrading affected packages to version 7.5.6, 8.0.2.

CVE-2026-44291 at a Glance

CVE Identifier CVE-2026-44291
GHSA Identifier GHSA-75px-5xx7-5xc7
Severity HIGH
CVSS v3.1 Base Score 8.1
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product Protobufjs
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 8.1

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:H/I:H/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 High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-44291

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

protobufjs fixed: 7.5.6 
npm install protobufjs@7.5.6
protobufjs fixed: 8.0.2 
npm install protobufjs@8.0.2
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 protobufjs

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-44291, inspect your project dependencies using npm:

npm ls protobufjs

Analyze the terminal output to locate any version of Protobufjs in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 7.5.6), your application is affected.

Note: The npm ls protobufjs 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-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution'), where the product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. In Protobufjs, 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

## Summary protobufjs used plain objects with inherited prototypes for internal type lookup tables used by generated encode and decode functions. If `Object.prototype` had already been polluted, those lookup tables could resolve attacker-controlled inherited properties as valid protobuf type information. This could cause attacker-controlled strings to be emitted into generated JavaScript code. ## Impact An attacker who can first trigger a prototype pollution vulnerability may be able to influence generated protobufjs encode or decode functions in a way that can lead to arbitrary JavaScript execution. This issue requires a separate prototype pollution primitive before protobufjs is invoked. Applications without a reachable prototype pollution primitive are not directly exploitable through this issue alone. ## Preconditions - The application or one of its dependencies must allow an attacker to pollute `Object.prototype`. - The polluted property must affect protobufjs internal type lookup behavior. - The application must use protobufjs functionality that generates encode or decode code for affected types. - The generated code path must be reached after the prototype pollution has occurred. ## Workarounds Avoid running affected versions in applications where attacker-controlled input can pollute `Object.prototype`. If immediate upgrade is not possible, remove or mitigate reachable prototype pollution primitives and isolate schema/message processing from untrusted application state.

CVE-2026-44291 Affected Protobufjs Versions

2 component(s)
Fixed Versions:
7.5.68.0.2
Product / Package Ecosystem Affected Versions Fixed Version
protobufjs
npm/protobufjs
npm
< 7.5.6
7.5.6
protobufjs
npm/protobufjs
npm
≥ 8.0.0
< 8.0.2
8.0.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-75px-5xx7-5xc7
NVD — CVE-2026-44291 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-44291
Protobufjs Source Repository REPOSITORY
https://github.com/protobufjs/protobuf.js
Protobufjs Release RELEASE
https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v7.5.6
Protobufjs Release RELEASE
https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.0.2

Frequently Asked Questions

What is CVE-2026-44291?
CVE-2026-44291 is a security vulnerability in Protobufjs involving Code generation gadget after prototype pollution under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which Protobufjs versions are affected?
Affected versions include releases prior to 7.5.6, 8.0.2 across affected packages: protobufjs.
What version fixes CVE-2026-44291?
Upgrading to 7.5.6, 8.0.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is protobufjs affected?
Yes, protobufjs is affected in releases prior to 7.5.6, 8.0.2. Upgrade your dependency to 7.5.6, 8.0.2 or later.
What is the CVSS score of CVE-2026-44291?
CVE-2026-44291 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-44291?
CVE-2026-44291 is classified under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.).
How can I check npm dependencies for CVE-2026-44291?
Run the dependency tree command: 'npm ls protobufjs'. 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-75px-5xx7-5xc7",
  "modified" : "2026-05-14T20:35:15Z",
  "published" : "2026-05-12T15:01:24Z",
  "aliases" : [ "CVE-2026-44291" ],
  "summary" : "protobuf.js: Code generation gadget after prototype pollution",
  "details" : "## Summary\n\nprotobufjs used plain objects with inherited prototypes for internal type lookup tables used by generated encode and decode functions. If `Object.prototype` had already been polluted, those lookup tables could resolve attacker-controlled inherited properties as valid protobuf type information.\n\nThis could cause attacker-controlled strings to be emitted into generated JavaScript code.\n\n## Impact\n\nAn attacker who can first trigger a prototype pollution vulnerability may be able to influence generated protobufjs encode or decode functions in a way that can lead to arbitrary JavaScript execution.\n\nThis issue requires a separate prototype pollution primitive before protobufjs is invoked.\n\nApplications without a reachable prototype pollution primitive are not directly exploitable through this issue alone.\n\n## Preconditions\n\n- The application or one of its dependencies must allow an attacker to pollute `Object.prototype`.\n- The polluted property must affect protobufjs internal type lookup behavior.\n- The application must use protobufjs functionality that generates encode or decode code for affected types.\n- The generated code path must be reached after the prototype pollution has occurred.\n\n## Workarounds\n\nAvoid running affected versions in applications where attacker-controlled input can pollute `Object.prototype`. If immediate upgrade is not possible, remove or mitigate reachable prototype pollution primitives and isolate schema/message processing from untrusted application state.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "protobufjs"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "7.5.6"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 7.5.5"
    }
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "protobufjs"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.0.0"
      }, {
        "fixed" : "8.0.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 8.0.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-75px-5xx7-5xc7"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44291"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/protobufjs/protobuf.js"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v7.5.6"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.0.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321", "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-12T15:01:24Z",
    "nvd_published_at" : "2026-05-13T16:16:55Z"
  }
}