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golang.org/x/crypto CVE-2026-56855

| EUVDEUVD-2026-70267 HIGH
Allocation of Resources Without Limits or Throttling (CWE-770)
2026-09-02
7.5
CVSS 3.1 · Vendor
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Severity by source

Vendor (CNA) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
vuln.today AI
7.5 HIGH

Network-reachable, no complexity or user interaction; PR:N reflects worst-case malicious-server-to-client attack; impact is availability-only.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative
Red Hat
5.3 MEDIUM
qualitative

Primary rating from Vendor (CNA).

CVSS VectorVendor

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

7
POC Analysis Generated
Sep 10, 2026 - 11:25 vuln.today
Analysis Updated
Sep 03, 2026 - 15:28 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Sep 03, 2026 - 15:22 vuln.today
cvss_changed
CVSS changed
Sep 03, 2026 - 15:22 NVD
7.5 (HIGH)
Patch available
Sep 02, 2026 - 21:17 EUVD
Analysis Generated
Sep 02, 2026 - 20:16 vuln.today
CVE Published
Sep 02, 2026 - 19:14 oss-security
HIGH

Description PRE-NVD

Disclosed via oss-security. NVD scoring and full description are pending.

AnalysisAI

Denial-of-service in the Go extended cryptography library's SSH package allows a malicious peer to deadlock an entire SSH connection by sending crafted RFC 4254 channel messages after a channel is established. All versions of golang.org/x/crypto/ssh below 0.56.0 are affected; the flaw manifests because unrecognized channel messages were buffered and allowed to block rather than being rejected as protocol errors. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
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Delivery
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Exploit
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Execution
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Persist
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Impact
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Vulnerability AssessmentAI

Exploitation Exploitation requires that an SSH channel has already been established between the victim application and the malicious peer - this means the SSH transport and, for server-side exploitation, authentication must have completed. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment CVSS 7.5 with AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H reflects the worst-case scenario: an attacker operating a malicious SSH server can deadlock any connecting client using the vulnerable library without requiring authentication on the attacker's side. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade golang.org/x/crypto to version 0.56.0 or later - the upstream fix is tracked at go.dev/cl/826524 and go.dev/issue/81316 and 81317. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, identify all internal applications and services that depend on golang.org/x/crypto/ssh and determine which are running versions before 0.56.0, with particular focus on production systems and automated infrastructure access. …

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
openSUSE Leap 16.0 Fixed
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise Micro 5.5 Affected
SUSE Linux Enterprise Module for Public Cloud 12 Affected
SUSE Linux Enterprise Server 12 Affected

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CVE-2026-56855 vulnerability details – vuln.today

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