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Findings

CVE-2026-56862

Limit handshake messages we are willing to accept post-handshake in crypto/tls

Published Aug 13, 2026 · updated Oct 10, 2026

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.

Timeline

Detection, updates, and resolution for this record.

  1. Aug 13, 2026 · Catalog

    Detected

    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.

  2. Oct 10, 2026 · Catalog

    Fix available

    Go stdlib 0 → 1.25.13

  3. Oct 10, 2026 · Catalog

    Updated

    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.

Affected

  • Go stdlib0 → 1.25.13

Sources

References