{"id":"GHSA-c8m5-c952-6cm4","aliases":["RUSTSEC-2026-0346"],"title":"Rustls: Session Debug formatting exposes TLS master secrets and resumption PSKs","summary":"Rustls: Session Debug formatting exposes TLS master secrets and resumption PSKs","severity":"medium","cvss":4,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:H/I:N/A:N","vendor":"rustls","product":"rustls","ecosystem":"rust","affected":["rustls < 0.23.46","rustls >= 0.24.0-dev.1, < 0.24.0-dev.2"],"patched":["rustls 0.23.46","rustls 0.24.0-dev.2"],"published":"2026-10-27","updated":"2026-10-27","sourceUpdated":"2026-10-27T16:15:05.354395696Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-c8m5-c952-6cm4","references":[{"url":"https://github.com/rustls/rustls/security/advisories/GHSA-c8m5-c952-6cm4"},{"url":"https://github.com/rustls/rustls/pull/3299"},{"url":"https://github.com/rustls/rustls/pull/3354"},{"url":"https://github.com/rustls/rustls/commit/dcdb9464d376f45f42a94a5f837cda1506449f23"},{"url":"https://github.com/rustls/rustls/commit/f5f7bf5078a7edcbd81a9e82a97f2bd14dc1c855"},{"url":"https://github.com/rustls/rustls"},{"url":"https://github.com/rustls/rustls/releases/tag/v/0.23.46"},{"url":"https://rustsec.org/advisories/RUSTSEC-2026-0346.html"},{"url":"https://github.com/advisories/GHSA-c8m5-c952-6cm4"}],"tags":["osv","rust","ghsa"],"cwe":["CWE-212"],"ingestedAt":"2026-10-27T16:11:58.699Z","slug":"GHSA-c8m5-c952-6cm4","body":"## Overview\n\n### Summary\n\nFormatting 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.\n\n### Details\n\nDerived 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).\n\n### Proof of concept\n\nCustom `ClientSessionStore` implementations could leak secret data by using the provided `Tls12ClientSessionValue` or `Tls13ClientSessionValue` in a way that triggers its implementation of the `Debug` trait.\n\n### Impact\n\nSuch store implementations could leak the master secret for the TLS connection.\n\n### Acknowledgement\nThanks to OpenAI [OutboundDisclosures@openai.com](mailto:OutboundDisclosures@openai.com) for the disclosure.\n\n## Affected packages\n\n- `rustls < 0.23.46`\n- `rustls >= 0.24.0-dev.1, < 0.24.0-dev.2`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `rustls 0.23.46`\n- `rustls 0.24.0-dev.2`","depth":"sunlit","depthScore":22,"depthScoreParts":{"impact":22,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}