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CVE-2026-56862— Limit handshake messages we are willing to accept post-handshake in crypto/tls

Quick assessment

Affected
Go standard library crypto/tls
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Google Go是美国Google公司开源的一款支持并发编程的脚本语言。 Google Go 1.25.13之前版本、1.26.6之前版本和1.27.0-rc.3之前版本存在资源管理错误漏洞，该漏洞源于握手消息状态处理不当，恶意客户端可不断发送KeyUpdate消息，导致服务器无限执行密钥派生操作，造成拒绝服务。

AI Predicted 5.9 Difficulty: Easy EPSS 0.46% · P38

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 3

VendorProduct Version RangeStatus
Go standard library crypto/tls < 1.25.13 affected
1.26.0-0< 1.26.6 affected
1.27.0-0< 1.27.0-rc.3 affected
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I. Basic Information for CVE-2026-56862

Vulnerability Information
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Vulnerability Title
Limit handshake messages we are willing to accept post-handshake in crypto/tls
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Google Go 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Google Go是美国Google公司开源的一款支持并发编程的脚本语言。 Google Go 1.25.13之前版本、1.26.6之前版本和1.27.0-rc.3之前版本存在资源管理错误漏洞，该漏洞源于握手消息状态处理不当，恶意客户端可不断发送KeyUpdate消息，导致服务器无限执行密钥派生操作，造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Go standard library crypto/tls 0 ~ 1.25.13 -

II. Public POCs for CVE-2026-56862

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III. Intelligence Information for CVE-2026-56862

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Patches & Fixes for CVE-2026-56862 (1)

Vendor Advisories for CVE-2026-56862 (3)

Same Patch Batch · Go standard library · 2026-08-13 · 6 CVEs total

CVE-2026-56859 Add recursion depth guard during decode in encoding/xml
CVE-2026-56858 Fix Javascript regexp context tracking in html/template
CVE-2026-56853 Apply ReadHeaderTimeout when doing unencrypted HTTP/2 check in net/http
CVE-2026-56860 Avoid quadratic complexity in resolvePath in net/url
CVE-2026-33818 Enforce maximum recursion depth in encoding/asn1

IV. Related Vulnerabilities

Same product: crypto/tls
Same vendor: Go standard library

V. Comments for CVE-2026-56862

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