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CVE-2026-56855— Prevent DoS on deadlocked established channel in golang.org/x/crypto/ssh

Quick assessment

Affected
golang.org/x/crypto golang.org/x/crypto/ssh
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 Golang是美国Google公司开源的一种支持高并发与系统级开发的静态编程语言。 Google Golang 0.56.0之前版本存在资源管理错误漏洞，该漏洞源于未正确处理RFC 4254信道消息，恶意对端可发送特制消息导致整个连接死锁。

AI Predicted 5.9 Difficulty: Moderate EPSS 0.38% · P31

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
golang.org/x/crypto golang.org/x/crypto/ssh < 0.56.0 affected
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I. Basic Information for CVE-2026-56855

Vulnerability Information
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Vulnerability Title
Prevent DoS on deadlocked established channel in golang.org/x/crypto/ssh
Source: CVE Program / CVE List V5
Vulnerability Description
Previously, after a channel has been established, a malicious peer could send crafted messages that would deadlock the entire connection. Now, we handle all RFC 4254 channel messages; global requests are handled explicitly. Then, treat all other messages as a protocol error and tear the connection down instead of buffering and blocking.
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 Golang 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Google Golang是美国Google公司开源的一种支持高并发与系统级开发的静态编程语言。 Google Golang 0.56.0之前版本存在资源管理错误漏洞，该漏洞源于未正确处理RFC 4254信道消息，恶意对端可发送特制消息导致整个连接死锁。
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
golang.org/x/crypto golang.org/x/crypto/ssh 0 ~ 0.56.0 -

II. Public POCs for CVE-2026-56855

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III. Intelligence Information for CVE-2026-56855

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Patches & Fixes for CVE-2026-56855 (2)

Vendor Advisories for CVE-2026-56855 (1)

Mailing List Discussions for CVE-2026-56855 (1)

IV. Related Vulnerabilities

Same product: golang.org/x/crypto/ssh
Same vendor: golang.org/x/crypto

V. Comments for CVE-2026-56855

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