Summary
npm Token Leak in npm
Affected versions of the npm package include the bearer token of the logged in user in every request made by the CLI, even if the request is not directed towards the user's active registry.
An attacker could create an HTTP server to collect tokens, and by various means including but not limited to install scripts, cause the npm CLI to make a request to that server, which would compromise the user's token.
This compromised token could be used to do anything that the user could do, including publishing new packages.
Impact
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.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
- Update npm with
npm install npm@latest -g - Revoke your Tokens
- Enable Two-Factor Authentication
Frequently Asked Questions
- What is CVE-2016-3956? CVE-2016-3956 is a high-severity security vulnerability in npm (npm), affecting versions <= 2.15.0. It is fixed in 2.15.1, 3.8.3.
- Which versions of npm are affected by CVE-2016-3956? npm (npm) versions <= 2.15.0 is affected.
- Is there a fix for CVE-2016-3956? Yes. CVE-2016-3956 is fixed in 2.15.1, 3.8.3. Upgrade to this version or later.
- Is CVE-2016-3956 exploitable, and should I be worried? Whether CVE-2016-3956 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-2016-3956 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-2016-3956?
- Upgrade
npmto 2.15.1 or later - Upgrade
npmto 3.8.3 or later
- Upgrade