Summary
Client TLS credentials sent raw to server in npm package nats
Nats is a Node.js client for the NATS messaging system.
Problem Description
Preview versions of two NPM packages and one Deno package from the NATS project contain an information disclosure flaw, leaking options to the NATS server; for one package, this includes TLS private credentials.
The connection configuration options in these JavaScript-based implementations were fully serialized and sent to the server in the client's CONNECT message, immediately after TLS establishment.
The nats.js client supports Mutual TLS and the credentials for the TLS client key are included in the connection configuration options; disclosure of the client's TLS private key to the server has been observed.
Most authentication mechanisms are handled after connection, instead of as part of connection, so other authentication mechanisms are unaffected.
For clarity: NATS account NKey authentication is NOT affected.
Neither the nats.ws nor the nats.deno clients support Mutual TLS: the affected versions listed below are those where the logic flaw is
present. We are including the nats.ws and nats.deno versions out of an abundance of caution, as library maintainers, but rate as minimal the likelihood of applications leaking sensitive data.
Affected versions
Security impact
- NPM package nats.js:
- mainline is unaffected
- beta branch is vulnerable from 2.0.0-201, fixed in 2.0.0-209
Logic flaw
NPM package nats.ws:
- status: preview
- flawed from 1.0.0-85, fixed in 1.0.0-111
Deno repository https://github.com/nats-io/nats.deno
- status: preview
- flawed in all git tags prior to fix
- fixed with git tag v1.0.0-9
Workaround
None
Impact
For deployments using TLS client certificates (for mutual TLS), private key material for TLS is leaked from the client application to the
server. If the server is untrusted (run by a third party), or if the client application also disables TLS verification (and so the true identity of the server is unverifiable) then authentication credentials are leaked.
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
Upgrade your package dependencies to fixed versions, and then reissue any TLS client credentials (with new keys, not just new certificates) and revoke the old ones.
Frequently Asked Questions
- What is GHSA-PRMC-5V5W-C465? GHSA-PRMC-5V5W-C465 is a critical-severity security vulnerability in nats (npm), affecting versions >= 2.0.0-201, <= 2.0.0-208. It is fixed in 2.0.0-209.
- Which versions of nats are affected by GHSA-PRMC-5V5W-C465? nats (npm) versions >= 2.0.0-201, <= 2.0.0-208 is affected.
- Is there a fix for GHSA-PRMC-5V5W-C465? Yes. GHSA-PRMC-5V5W-C465 is fixed in 2.0.0-209. Upgrade to this version or later.
- Is GHSA-PRMC-5V5W-C465 exploitable, and should I be worried? Whether GHSA-PRMC-5V5W-C465 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 GHSA-PRMC-5V5W-C465 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 GHSA-PRMC-5V5W-C465? Upgrade
natsto 2.0.0-209 or later.