CVE-2026-56862: Limit handshake messages we are willing to accept post-handshake in crypto/tls
Handshake messages, such as KeyUpdate, are always considered as state-advancing, regardless of whether a handshake has been completed or not. As a result, a malicious client can keep sending KeyUpdate messages to force the server to keep performing key derivation operations indefinitely.
Other sources
Limit handshake messages we are willing to accept post-handshake in crypto/tls
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
alpine/goto a version that resolves this vulnerability.Fixed in 1.26.8-r0 - Compensating control
Limit the number of post-handshake TLS handshake messages accepted by the server (specifically include KeyUpdate) to prevent a malicious client from forcing indefinite key derivation operations.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-56862?
CVE-2026-56862 has a risk level of 36.
How do I fix CVE-2026-56862?
To mitigate CVE-2026-56862, limit the handshake messages accepted post-handshake as necessary in the crypto/tls implementation.
What impact does CVE-2026-56862 have on my application?
CVE-2026-56862 allows a malicious client to send indefinite KeyUpdate messages, which can consume server resources and affect performance.
Is CVE-2026-56862 a critical vulnerability?
While CVE-2026-56862 has a significant risk score, the criticality depends on its specific implementation within your application and environment.
When was CVE-2026-56862 published?
CVE-2026-56862 was published on August 13, 2026.