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Vulnerabilities

Security incident · GHSA-c8m5-c952-6cm4

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

Published Oct 27, 2026 · catalog updated Oct 27, 2026 · Rustls: Session Debug formatting

Last checked Oct 29, 2026, 8 days ago.

Open the advisory

Exploitation likelihood is not on this record for GHSA-c8m5-c952-6cm4. A missing EPSS score is not a low risk. Compare Rustls: Session Debug formatting with the linked advisory before you change production.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Rustls: Session Debug formatting).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
  • EPSS is missing. A missing score is not a low risk.
Severity
Medium4.0
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
Awaiting synchronization with FIRST
Remediation
Version ranges on file
Affected products
crates.io rustls · rust rustls

### 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](https://github.com/rustls/rustls/blob/99f2358cae2954837dbb866faf6727de75489ab9/SECURITY.md#boundary-public-api). ### Proof of concept Custom implementations could leak secret data by using the provided or in a way that triggers its implementation of the trait. ### Impact Such store implementations could leak the master secret for the TLS connection. ### Acknowledgement Thanks to OpenAI [OutboundDisclosures@openai.com](mailto:OutboundDisclosures@openai.com) for the disclosure.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • crates.io rustls0 → 0.23.46
  • crates.io rustls0.24.0-dev.1 → 0.24.0-dev.2
  • rust rustls< 0.23.46
  • rust rustls>= 0.24.0-dev.1, < 0.24.0-dev.2

How to fix GHSA-c8m5-c952-6cm4

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

Exploitation likelihood is not on this record for GHSA-c8m5-c952-6cm4. A missing EPSS score is not a low risk. Compare Rustls: Session Debug formatting with the linked advisory before you change production.

Which versions are affected?

Compare what you have installed with 0 → 0.23.46, 0.24.0-dev.1 → 0.24.0-dev.2, < 0.23.46, >= 0.24.0-dev.1, < 0.24.0-dev.2. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-212: Improper Removal of Sensitive Information Before Storage or Transfer. EPSS is not on this record yet. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 27, 2026 · GitHub Advisory Database

    Detected

    ### 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 sessi

  2. Oct 27, 2026 · GitHub Advisory Database

    Updated

    ### 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 sessi

  3. Oct 27, 2026 · GitHub Advisory Database

    Fix available

    rustls fixed in 0.23.46; rustls fixed in 0.24.0-dev.2

  4. Oct 27, 2026 · GitHub Advisory Database

    Fix available

    rustls fixed in 0.23.46

  5. Oct 27, 2026 · GitHub Advisory Database

    Fix available

    rustls fixed in 0.24.0-dev.2

  6. Oct 27, 2026 · GitHub Advisory Database

    Updated

    ### 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 sessi

Sources

References

Freshness

Last verified in this catalog Oct 27, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • GitHub Advisory DatabaseOct 29, 2026
  • OpenSSF OSV / OSV ScannerOct 29, 2026