GHSA-c8m5-c952-6cm4 Rustls: Session Debug formatting exposes TLS master secrets and resumption PSKs
- Exploited in the wild
- Not known
- Fix
- Available
What is GHSA-c8m5-c952-6cm4?
GHSA-c8m5-c952-6cm4 is a vulnerability in rustls, published on 14 Oct 2026.
Official description
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 [email protected] for the disclosure.
Which versions are affected by GHSA-c8m5-c952-6cm4?
5 open source packages ship an affected version, including rustls.
| Package | Affected | Fixed in |
|---|---|---|
rustls crates.io | All versions | 0.23.46 |
rustls crates.io | All versions | 0.23.46 |
rustls crates.io | From 0.21.0 | 0.23.46 |
rustls crates.io | From 0.24.0-dev.1 | 0.24.0-dev.2 |
rustls crates.io | From 0.24.0-dev.1 | 0.24.0-dev.2 |
How do I fix GHSA-c8m5-c952-6cm4?
Upgrade rustls to a fixed version for your release line: 0.23.46 or 0.24.0-dev.2.
Is GHSA-c8m5-c952-6cm4 being exploited?
There is no known exploitation of GHSA-c8m5-c952-6cm4 in the wild and no public exploit code.
Sources
Also known as RUSTSEC-2026-0346.