RUSTSEC-2026-0285 (GHSA-2MJX-QC3C-RQVC)
Vulnerability from osv_rustsec – Published: 2026-09-14 12:00 – Updated: 2026-10-12 17:47 – Source websiteRustls 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": "2026-10-12T17:47:59Z",
"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": "WEB",
"url": "https://github.com/rustls/rustls/pull/3265"
}
],
"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"
}
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- 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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.