Protection Mechanism Failure Affecting github.com/refraction-networking/utls package, versions <1.7.0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published28 Apr 2025
- disclosed24 Apr 2025
- creditUnknown
Introduced: 24 Apr 2025
CVE-2026-26994 (opens in a new tab)How to fix?
Upgrade github.com/refraction-networking/utls to version 1.7.0 or higher.
Overview
Affected versions of this package are vulnerable to Protection Mechanism Failure in the ClientHandshake() function, which handles ClientHello messages, and in particular the serverHello.random field. An attacker can downgrade the TLS connection from TLS 1.3 by removing the SupportedVersions extension and thereby bypass checking for a downgrade canary, which could facilitate traffic interception and MitM attacks. Protection against TLS downgrade is required as part of RFC 8446 Section 4.1.3.