Sensitive data exposure in NATS

Overview

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
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.

Recommendation

Upgrade to version 2.0.0-209 or later

References

• www.github.com/advisories/GHSA-82rf-q3pr-4f6p
• GitHub Advisory