GHSA-c8m5-c952-6cm4 — Rustls: Session Debug formatting exposes TLS master secrets and resumption PSKs

The advisory, in context

Summary

Formatting a client session value with Debug exposes its TLS 1.2 master secret or TLS 1.3 resumption PSK. A custom session store that logs these values can disclose keys to readers of the logs. Ordinary connection and built-in cache diagnostics remain redacted, and the session-store interface already warns that its values are sensitive.

Details

Derived formatters traverse the session's secret-bearing fields. This conflicts with the project's explicit key-material redaction policy.

Proof of concept

Custom ClientSessionStore implementations could leak secret data by using the provided Tls12ClientSessionValue or Tls13ClientSessionValue in a way that triggers its implementation of the Debug trait.

Impact

Such store implementations could leak the master secret for the TLS connection.

Acknowledgement

Thanks to OpenAI OutboundDisclosures@openai.com for the disclosure.

Affected packages

Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.

rustls crates.io

Semantic versions

Earlier releases before 0.23.46

Fixed in 0.23.46

View affected-version evidence

{
  "ranges": [
    {
      "events": [
        {
          "introduced": "0"
        },
        {
          "fixed": "0.23.46"
        }
      ],
      "type": "SEMVER"
    }
  ],
  "versions": []
}

rustls crates.io

Semantic versions

From 0.24.0-dev.1 before 0.24.0-dev.2

Fixed in 0.24.0-dev.2

View affected-version evidence

{
  "ranges": [
    {
      "events": [
        {
          "introduced": "0.24.0-dev.1"
        },
        {
          "fixed": "0.24.0-dev.2"
        }
      ],
      "type": "SEMVER"
    }
  ],
  "versions": []
}

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Rustls: Session Debug formatting exposes TLS master secrets and resumption PSKs