Rustls before 0.23.46 and 0.24.0-dev.1 before 0.24.0-dev.2 contains an information disclosure vulnerability where derived Debug formatting of client session values exposes secret key material. Custom ClientSessionStore implementations that log Tls12ClientSessionValue or Tls13ClientSessionValue can leak TLS 1.2 master secrets or TLS 1.3 resumption PSKs to log readers.

Rustls before 0.23.46 and 0.24.0-dev.1 before 0.24.0-dev.2 contains an information disclosure vulnerability where derived Debug formatting of client session values exposes secret key material. Custom ClientSessionStore implementations that log Tls12ClientSessionValue or Tls13ClientSessionValue can leak TLS 1.2 master secrets or TLS 1.3 resumption PSKs to log readers.

Affected: crates.io: rustls

The `Debug` implementations of `Tls12ClientSessionValue` and `Tls13ClientSessionValue` were derived, and so included the TLS 1.2 master secret or TLS 1.3 resumption PSK in their output.

Custom `ClientSessionStore` implementations that format these values with `Debug` (for example, when logging) could disclose these secrets to readers of the logs. This conflicts with rustls's [key-material redaction policy](https://github.com/rustls/rustls/blob/99f2358cae2954837dbb866faf6727de75489ab9/SECURITY.md#boundary-public-api).

Ordinary connection and built-in session cache `Debug` output is redacted and is not affected.

Affected: Ubuntu:24.04:LTS: rust-rustls, Ubuntu:26.10: rust-rustls, Ubuntu:26.04:LTS: rust-rustls

Rustls before 0.23.46 and 0.24.0-dev.1 before 0.24.0-dev.2 contains an information disclosure vulnerability where derived Debug formatting of client session values exposes secret key material. Custom ClientSessionStore implementations that log Tls12ClientSessionValue or Tls13ClientSessionValue can leak TLS 1.2 master secrets or TLS 1.3 resumption PSKs to log readers.