uTLS ServerHellos are accepted without checking TLS 1.3 downgrade canaries
Résumé
uTLS ServerHellos are accepted without checking TLS 1.3 downgrade canaries
Description d'origine
La description telle que publiée par la source (souvent en anglais).
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.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
État des correctifs par distribution
Paquets corrigés publiés par chaque distribution pour cette CVE
- Debian DEBIAN-CVE-2026-26994 golang-refraction-networking-utls
- Ubuntu UBUNTU-CVE-2026-26994 golang-refraction-networking-utls
Références
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- patch github.com
- patch github.com
- report github.com