DEBIAN-CVE-2026-26994
uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. In versions 1.6.7 and below, uTLS did not implement the TLS 1.3 downgrade protection mechanism specified in RFC 8446 Section 4.1.3 when using a uTLS ClientHello spec. This allowed an active network adversary to downgrade TLS 1.3 connections initiated by a uTLS client to a lower TLS version (e.g., TLS 1.2) by modifying the ClientHello message to exclude the SupportedVersions extension, causing the server to respond with a TLS 1.2 ServerHello (along with a downgrade canary in the ServerHello random field). Because uTLS did not check the downgrade canary in the ServerHello random field, clients would accept the downgraded connection without detecting the attack. This attack could also be used by an active network attacker to fingerprint uTLS connections. This issue has been fixed in version 1.7.0.
DEBIAN-CVE-2026-26994
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:DEBIAN-CVE-2026-26994
golang-refraction-networking-utls
Source reference: /affected/0/package/name
- Affected versions
- 1.2.1-2
Source reference:
/affected/0/versions1.2.1-3Source reference:
/affected/0/versions1.2.1-3.1Source reference:
/affected/0/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
golang-refraction-networking-utls
Source reference: /affected/1/package/name
- Affected versions
- 1.2.1-3.1
Source reference:
/affected/1/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
golang-refraction-networking-utls
Source reference: /affected/2/package/name
- Affected versions
- 1.2.1-3.1
Source reference:
/affected/2/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "golang-refraction-networking-utls",
"purl": "pkg:deb/debian/golang-refraction-networking-utls?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"1.2.1-2",
"1.2.1-3",
"1.2.1-3.1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-26994.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "golang-refraction-networking-utls",
"purl": "pkg:deb/debian/golang-refraction-networking-utls?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"1.2.1-3.1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-26994.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "golang-refraction-networking-utls",
"purl": "pkg:deb/debian/golang-refraction-networking-utls?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"1.2.1-3.1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-26994.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #56307 · Revision 1
- Added to Heist Feed
- Publisher date