CVE-2026-26994
ServerHellos are accepted without checking TLS 1.3 downgrade canaries in github.com/refraction-networking/utls
描述
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.
如何修補 CVE-2026-26994
要修補 CVE-2026-26994,請將受影響套件升級到下列已修補版本。
- —未列出修補版本
- —升級至 1.7.0 或更新版本
- —升級至 1.7.0 或更新版本
CVE-2026-26994 正在被利用嗎?
低 — EPSS 為 0.3%,目前沒有觀察到大規模利用活動。
受影響套件(3)
- from 0
- from 0, < 1.7.0
- >= 1.0.0, < 1.7.0
CVSS 分數
| 來源 | 版本 | 嚴重程度 | 向量 |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N |