CVE-2026-55451: gettext-converter Prototype Pollution Vulnerability

MODERATE
Advisory Identifier: GHSA-f4jp-rw7w-ccwg
Share
CWE-1321
Published
Advisory Summary

CVE-2026-55451 is a MODERATE prototype pollution vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting gettext-converter libraries in the npm ecosystem. The issue involves prototype pollution in js2i18next() via crafted translation keys. Remediation is available by upgrading affected packages to version 1.3.3.

CVE-2026-55451 at a Glance

CVE Identifier CVE-2026-55451
GHSA Identifier GHSA-f4jp-rw7w-ccwg
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product gettext-converter
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-55451

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

gettext-converter fixed: 1.3.3 
npm install gettext-converter@1.3.3
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 gettext-converter

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-55451, inspect your project dependencies using npm:

npm ls gettext-converter

Analyze the terminal output to locate any version of gettext-converter in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.3.3), your application is affected.

Note: The npm ls gettext-converter 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 gettext-converter, 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 `js2i18next()` is vulnerable to prototype pollution. When converting translations, it splits nested keys on the key separator (default `##`) and uses each segment as a dynamic object key while building the output object. A key whose segment is `__proto__` (e.g. `__proto__##gcPolluted`) causes the converter to resolve `Object.prototype` as the nested write target and assign the translated value onto it, polluting `Object.prototype` for the whole runtime. Any application that converts translation data (PO / i18next JS objects) originating from an untrusted or user-controlled source is affected. Prototype pollution can lead to denial of service and, depending on the surrounding application, may enable further attacks. ### Patches Fixed in `gettext-converter@1.3.3`. Key segments equal to `__proto__`, `constructor`, or `prototype` are now rejected before being used as dynamic object keys. ### Workarounds Upgrade to `1.3.3`. If upgrading is not immediately possible, sanitize/validate translation keys before passing them to `js2i18next()` and reject any key whose `##`-separated segments include `__proto__`, `constructor`, or `prototype`.

CVE-2026-55451 Affected gettext-converter Versions

1 component(s)
Fixed Versions:
1.3.3
Product / Package Ecosystem Affected Versions Fixed Version
gettext-converter
npm/gettext-converter
npm
< 1.3.3
1.3.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/locize/gettext-converter/security/advisories/GHSA-f4jp-rw7w-ccwg
gettext-converter Source Repository REPOSITORY
https://github.com/locize/gettext-converter/issues/15
Security Fix Commit FIX COMMIT
https://github.com/locize/gettext-converter/commit/df90c3b93e51faef68891d97b626544f619c5b31
gettext-converter Source Repository REPOSITORY
https://github.com/locize/gettext-converter
gettext-converter Release RELEASE
https://github.com/locize/gettext-converter/releases/tag/v1.3.3

Frequently Asked Questions

What is CVE-2026-55451?
CVE-2026-55451 is a security vulnerability in gettext-converter involving Prototype pollution in js2i18next() via crafted translation keys under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which gettext-converter versions are affected?
Affected versions include releases prior to 1.3.3 across affected packages: gettext-converter.
What version fixes CVE-2026-55451?
Upgrading to 1.3.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is gettext-converter affected?
Yes, gettext-converter is affected in releases prior to 1.3.3. Upgrade your dependency to 1.3.3 or later.
What CWE is associated with CVE-2026-55451?
CVE-2026-55451 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-2026-55451?
Run the dependency tree command: 'npm ls gettext-converter'. 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-f4jp-rw7w-ccwg",
  "modified" : "2026-08-20T20:11:13Z",
  "published" : "2026-08-20T20:11:13Z",
  "aliases" : [ "CVE-2026-55451" ],
  "summary" : "gettext-converter: Prototype pollution in js2i18next() via crafted translation keys",
  "details" : "### Impact\n\n`js2i18next()` is vulnerable to prototype pollution. When converting translations, it splits nested keys on the key separator (default `##`) and uses each segment as a dynamic object key while building the output object. A key whose segment is `__proto__` (e.g. `__proto__##gcPolluted`) causes the converter to resolve `Object.prototype` as the nested write target and assign the translated value onto it, polluting `Object.prototype` for the whole runtime.\n\nAny application that converts translation data (PO / i18next JS objects) originating from an untrusted or user-controlled source is affected. Prototype pollution can lead to denial of service and, depending on the surrounding application, may enable further attacks.\n\n### Patches\n\nFixed in `gettext-converter@1.3.3`. Key segments equal to `__proto__`, `constructor`, or `prototype` are now rejected before being used as dynamic object keys.\n\n### Workarounds\n\nUpgrade to `1.3.3`. If upgrading is not immediately possible, sanitize/validate translation keys before passing them to `js2i18next()` and reject any key whose `##`-separated segments include `__proto__`, `constructor`, or `prototype`.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "gettext-converter"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.3.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/locize/gettext-converter/security/advisories/GHSA-f4jp-rw7w-ccwg"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/locize/gettext-converter/issues/15"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/locize/gettext-converter/commit/df90c3b93e51faef68891d97b626544f619c5b31"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/locize/gettext-converter"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/locize/gettext-converter/releases/tag/v1.3.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-20T20:11:13Z",
    "nvd_published_at" : null
  }
}