CVE-2026-56862

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

Published Aug 13, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Ubuntu USN Ubuntu USN USN-8935-1 Go vulnerabilities
History
Type Values Removed Values Added
Weaknesses CWE-770
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Weaknesses CWE-1003
CWE-1015
CWE-606
Type Values Removed Values Added
First Time appeared Go Standard Library
Go Standard Library crypto Tls
Vendors & Products Go Standard Library
Go Standard Library crypto Tls
Type Values Removed Values Added
Description 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.
Title Limit handshake messages we are willing to accept post-handshake in crypto/tls
References

Sources

Status
PUBLISHED
Assigner
Go
Published
Updated
Aug 14, 2026, 3:29 PM
Reserved
Jun 23, 2026, 3:10 PM
Status
Awaiting Analysis
Published
Aug 13, 2026, 10:17 PM
Modified
Oct 24, 2026, 4:10 PM
Severity
Important
Public date
Aug 13, 2026, 9:58 PM