# Rustls: TLS 1.3 handshake messages incorrectly accepted across encryption level boundaries

Advisory record · `GHSA-2mjx-qc3c-rqvc`

- **Identifiers:** `GHSA-2mjx-qc3c-rqvc` · `CVE-2026-123613` · `RUSTSEC-2026-0285`
- **State:** Confirmed
- **Severity:** CVSS 6.9 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-20](https://cwe.mitre.org/data/definitions/20.html)
- **Tags:** [CWE-20](https://agentprime.io/advisories/tag/cwe-20.md)
- **Published:** 5 Oct 2026
- **Updated:** 8 Nov 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 5 Oct 2026, 23:30 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `rustls` (crates.io): affected `>=0.23.13, <0.23.45`; fixed in `0.23.45`

## Machine-written summary

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

> Rustls versions 0.23.13 through 0.23.44 accept TLS 1.3 handshake messages sent at the wrong encryption level when they follow a key-changing message in the same record. An attacker in a network position can inject plaintext handshake messages that rustls accepts, but cannot use this to alter or complete a handshake because the transcript remains authenticated. Upgrade to rustls 0.23.45, which contains the fix.

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

- 6.9 Medium, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`, from CNA (VulnCheck)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0016, the 4th percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## 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-2mjx-qc3c-rqvc)
- 8 Nov 2026, 01:45 UTC: [Confirmed by the CVE List](https://www.cve.org/CVERecord?id=CVE-2026-123613)
- 8 Nov 2026, 02:21 UTC: [Confirmed by NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-123613)

## Sources

- [GitHub Advisory Database: GHSA-2mjx-qc3c-rqvc](https://github.com/advisories/GHSA-2mjx-qc3c-rqvc)
- [OSV: GHSA-2mjx-qc3c-rqvc](https://osv.dev/vulnerability/GHSA-2mjx-qc3c-rqvc)
- <https://github.com/rustls/rustls/security/advisories/GHSA-2mjx-qc3c-rqvc>
- <https://github.com/rustls/rustls/pull/3265>
- <https://github.com/golang/go/commit/5046bdf8a612b35a2c1a9e168054c1d5c65e7dd7>
- <https://github.com/rustls/rustls/commit/98456aea708a7e3c6151e00ca2d4428e7a58257a>
- <https://github.com/rustls/rustls>
- <https://github.com/rustls/rustls/releases/tag/v/0.23.45>
- <https://rustsec.org/advisories/RUSTSEC-2026-0285.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-2mjx-qc3c-rqvc>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

---

The web page: <https://agentprime.io/advisories/GHSA-2mjx-qc3c-rqvc/>. Everything for agents: <https://agentprime.io/llms.txt>.