RUSTSEC-2026-0285
Vulnerability from osv_rustsec
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 (CVE-2025-61730).
| URL | Type | |
|---|---|---|
{
"affected": [
{
"database_specific": {
"categories": [
"crypto-failure"
],
"cvss": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"informational": null
},
"ecosystem_specific": {
"affected_functions": null,
"affects": {
"arch": [],
"functions": [],
"os": []
}
},
"package": {
"ecosystem": "crates.io",
"name": "rustls",
"purl": "pkg:cargo/rustls"
},
"ranges": [
{
"events": [
{
"introduced": "0.23.13"
},
{
"fixed": "0.23.45"
}
],
"type": "SEMVER"
}
],
"versions": []
}
],
"aliases": [
"GHSA-2mjx-qc3c-rqvc"
],
"database_specific": {
"license": "CC0-1.0"
},
"details": "Rustls accepted TLS 1.3 handshake messages sent at the wrong encryption level\nwhen they followed a key-changing message in the same record. For example,\na plaintext `EncryptedExtensions` message packed into the same record as the\n`ServerHello` was accepted.\n\nRFC 8446 section 5.1 requires that handshake messages do not span key changes,\nand that implementations terminate the connection with an \"unexpected_message\"\nalert if they do.\n\nThe handshake transcript is still authenticated, so a network-position attacker\ncannot use this to alter or complete a handshake; the practical effect is that\na peer could send handshake messages that should be encrypted in plaintext\nwithout rustls rejecting the connection.\n\nThis is functionally the same bug as Go\u0027s\n[GO-2026-4340](https://pkg.go.dev/vuln/GO-2026-4340) (CVE-2025-61730).",
"id": "RUSTSEC-2026-0285",
"modified": "2026-09-14T16:06:06Z",
"published": "2026-09-14T12:00:00Z",
"references": [
{
"type": "PACKAGE",
"url": "https://crates.io/crates/rustls"
},
{
"type": "ADVISORY",
"url": "https://rustsec.org/advisories/RUSTSEC-2026-0285.html"
},
{
"type": "ADVISORY",
"url": "https://github.com/rustls/rustls/security/advisories/GHSA-2mjx-qc3c-rqvc"
}
],
"related": [],
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "TLS 1.3 handshake messages incorrectly accepted across encryption level boundaries"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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