Summary
gettext-converter: Prototype pollution in js2i18next() via crafted translation 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.
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.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in [email protected]. Key segments equal to __proto__, constructor, or prototype are now rejected before being used as dynamic object keys.
Frequently Asked Questions
- What is CVE-2026-55451? CVE-2026-55451 is a medium-severity security vulnerability in gettext-converter (npm), affecting versions < 1.3.3. It is fixed in 1.3.3.
- Which versions of gettext-converter are affected by CVE-2026-55451? gettext-converter (npm) versions < 1.3.3 is affected.
- Is there a fix for CVE-2026-55451? Yes. CVE-2026-55451 is fixed in 1.3.3. Upgrade to this version or later.
- Is CVE-2026-55451 exploitable, and should I be worried? Whether CVE-2026-55451 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-55451 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-55451? Upgrade
gettext-converterto 1.3.3 or later.