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

Advisory record · `GHSA-c8m5-c952-6cm4`

- **Identifiers:** `GHSA-c8m5-c952-6cm4` · `RUSTSEC-2026-0346`
- **State:** Confirmed
- **Severity:** CVSS 4.0 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-212](https://cwe.mitre.org/data/definitions/212.html)
- **Tags:** [CWE-212](https://agentprime.io/advisories/tag/cwe-212.md)
- **Published:** 27 Oct 2026
- **Updated:** 27 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 27 Oct 2026, 16:08 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `rustls` (crates.io): affected `<0.23.46 || >=0.24.0-dev.1, <0.24.0-dev.2`; fixed in `0.23.46`, `0.24.0-dev.2`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Rustls versions below 0.23.46, and 0.24.0-dev.1 only, are affected; the fixed versions are 0.23.46 and 0.24.0-dev.2. Debug formatting of TLS 1.2 and TLS 1.3 client session values can expose the TLS master secret or resumption PSK. Exposure requires a custom session store that formats these values into logs, and a reader of those logs could then recover keys. Upgrade to 0.23.46 or 0.24.0-dev.2.

Written 3 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 4.0 Medium, CVSS 3.1: `CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:H/I:N/A:N`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** No score.

## Timeline

- 31 Oct 2026, 14:24 UTC: First seen by agentprime
- 31 Oct 2026, 14:24 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-c8m5-c952-6cm4)

## Sources

- [GitHub Advisory Database: GHSA-c8m5-c952-6cm4](https://github.com/advisories/GHSA-c8m5-c952-6cm4)
- [OSV: GHSA-c8m5-c952-6cm4](https://osv.dev/vulnerability/GHSA-c8m5-c952-6cm4)
- <https://github.com/rustls/rustls/security/advisories/GHSA-c8m5-c952-6cm4>
- <https://github.com/rustls/rustls/pull/3299>
- <https://github.com/rustls/rustls/pull/3354>
- <https://github.com/rustls/rustls/commit/dcdb9464d376f45f42a94a5f837cda1506449f23>
- <https://github.com/rustls/rustls/commit/f5f7bf5078a7edcbd81a9e82a97f2bd14dc1c855>
- <https://github.com/rustls/rustls>
- <https://github.com/rustls/rustls/releases/tag/v/0.23.46>
- <https://rustsec.org/advisories/RUSTSEC-2026-0346.html>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-c8m5-c952-6cm4>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-c8m5-c952-6cm4/>. Everything for agents: <https://agentprime.io/llms.txt>.