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NATS TLS certificate common name validation bypass

GHSA-wvc4-j7g5-4f79

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (nats 0.24.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • crates.io nats

    Affected
    >= 0.9.0, <= 0.24.0
    Fixed in
    0.24.1

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
not scored
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

The NATS official Rust clients are vulnerable to MitM when using TLS. A fix for the nats crate hasn't been released yet. Since the nats crate is going to be deprecated anyway, consider switching to async-nats = 0.29 which already fixed this vulnerability. The common name of the server's TLS certificate is validated against the hostname provided by the server's plaintext INFO message during the initial connection setup phase. A MitM proxy can tamper with the host field's value by substituting it with the common name of a valid certificate it controls, fooling the client into accepting it. Reproduction steps 1. The NATS Rust client tries to establish a new connection 2. The connection is intercepted by a MitM proxy 3. The proxy makes a separate connection to the NATS server 4. The NATS server replies with an INFO message 5. The proxy reads the INFO, alters the host JSON field and passes the tampered INFO back to the client 6. The proxy upgrades the client connection to TLS, presenting…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-wvc4-j7g5-4f79

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-wvc4-j7g5-4f79

Advisory: NATS TLS certificate common name validation bypass
IDs: GHSA-wvc4-j7g5-4f79
Record: https://patchnext.com/advisories/ghsa-wvc4-j7g5-4f79 (revision 1, source checked 26 Oct 2026, 15:37 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nats 0.24.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io nats: affected >= 0.9.0, <= 0.24.0; fixed in 0.24.1

## Suggested inspection (read-only)
- crates.io nats: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on nats.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-wvc4-j7g5-4f79 (GitHub-reviewed advisory GHSA-wvc4-j7g5-4f79 lists affected ranges: crates.io nats >=0.9.0 <=0.24.0)

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