TLS 1.3 handshake messages incorrectly accepted across encryption level boundaries

{
  "id": "50a3f824536c47e68ae96d4ce25ed6cdae2c09010838835fcdf86afba9659ef4",
  "url": "https://osv.dev/vulnerability/RUSTSEC-2026-0285",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "TLS 1.3 handshake messages incorrectly accepted across encryption level boundaries",
    "summary": "Rustls accepted TLS 1.3 handshake messages sent at the wrong encryption level when they followed a key-changing message in the same record. For example, a plaintext `EncryptedExtensions` message packed into the same record as the `ServerHello` was accepted. RFC 8446 section 5.1 requires that handshake messages do not span key changes, and that implementations terminate the connection with an \"unexpected_message\" alert if they do. The handshake transcript is still authenticated, so a network-position attacker cannot use this to alter or complete a handshake; the practical effect is that a peer could send handshake messages that should be encrypted in plaintext without rustls rejecting the connection. This is functionally the same bug as Go's [GO-2026-4340](https://pkg.go.dev/vuln/GO-2026-4340) (CVE-2025-61730).",
    "evidence": "osv:RUSTSEC-2026-0285",
    "products": [
      {
        "name": {
          "value": "rustls",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "0.23.45",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "RUSTSEC-2026-0285",
      "aliases": [
        "GHSA-2mjx-qc3c-rqvc",
        "RUSTSEC-2026-0285"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0.23.13"
                },
                {
                  "fixed": "0.23.45"
                }
              ]
            }
          ],
          "package": {
            "name": "rustls",
            "purl": "pkg:cargo/rustls",
            "ecosystem": "crates.io"
          },
          "database_specific": {
            "cvss": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
            "source": "https://github.com/rustsec/advisory-db/blob/osv/crates/RUSTSEC-2026-0285.json",
            "categories": [
              "crypto-failure"
            ],
            "informational": null
          },
          "ecosystem_specific": {
            "affects": {
              "os": [],
              "arch": [],
              "functions": []
            },
            "affected_functions": null
          }
        }
      ],
      "modified": "2026-10-12T18:00:10.944958251Z",
      "provider": "osv",
      "references": [
        "https://crates.io/crates/rustls",
        "https://rustsec.org/advisories/RUSTSEC-2026-0285.html",
        "https://github.com/rustls/rustls/pull/3265"
      ],
      "provider_metadata": {
        "license": "CC0-1.0"
      }
    },
    "related_cves": [],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 306407,
  "published_at": "2026-09-14T12:00:00+00:00"
}