CVE-2026-56862
CVE
High
High Impactcrypto/tls: Uncontrolled Key Derivation via Repeated KeyUpdate Messages
Exploitable
This vulnerability is exploitable in typical deployments. Upgrade to the fixed version as soon as possible.
Component
Go standard library (crypto/tls)
Disclosed
Aug 14, 2026
Description
Go’s
crypto/tls package treats TLS 1.3 KeyUpdate messages as state-advancing
regardless of whether the handshake has completed, and does not limit how many a
peer can send. A malicious client can keep transmitting KeyUpdate messages to
force the server to repeatedly perform expensive key derivation operations,
consuming CPU for as long as the connection stays open. The fix bounds how often
KeyUpdate-triggered rekeying is honored.Version summary
Community Edition
2.13.9
addresses this advisory
Affected CE versions
>= 2.0, < 2.13.9
Enterprise Edition
2.13.7
addresses this advisory
Affected EE versions
>= 2.0, < 2.13.7
Upgrade to the addressed version or later to remediate this vulnerability.