What is the CVSS score of EUVD-2026-31394?

EUVD-2026-31394 has a CVSS 3.1 base score of 6.3 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L. EPSS exploitation probability: 0.0%.

Is there a public PoC exploit available for EUVD-2026-31394?

Yes, a public proof-of-concept exploit is available for EUVD-2026-31394. Prioritise patching immediately. EPSS: 0.0%.

Is there a patch available for EUVD-2026-31394?

Yes, a patch is available for EUVD-2026-31394. Update the affected software to the latest version immediately.

golang.org/x/crypto EUVD-2026-31394

| CVE-2026-39828 MEDIUM

Improper Certificate Validation (CWE-295)

2026-05-22 Go

GHSA-45gg-vh54-h5m9

Information Disclosure Golang Org X Crypto Ssh Golang Org X Crypto

6.3

CVSS 3.1 · Vendor: Go

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Obtain valid first-factor SSH credentials
Delivery

Connect to target Go SSH server running vulnerable golang.org/x/crypto/ssh
Exploit

Authenticate first factor, triggering PartialSuccessError with certificate Permissions silently discarded
Execution

Complete second-factor authentication
Persist

Receive SSH session with certificate restrictions (e.g., force-command) absent
Impact

Execute arbitrary commands beyond intended access scope

Vulnerability Assessment

Weakness	CWE CWE-295 OWASP Top 10:2025 A07:2025 - Authentication Failures ASVS 5.0 V12 - Secure Communication Certificate validation
Exploitation Conditions	Exploitation requires all of the following to be true simultaneously: (1) the SSH server is built using golang.org/x/crypto/ssh at a version below 0.52.0; (2) the server implements multi-factor authentication using the PartialSuccessError mechanism; (3) the server's authentication callback returns non-nil Permissions alongside PartialSuccessError during the MFA sequence; (4) the attacker possesses valid first-factor credentials (CVSS PR:L confirms authentication is required). Exploitation is limited by the attacker needing prior authenticated access, and by the vulnerability only materializing when certificate Permissions are the enforced access control boundary. Servers not using MFA, not using certificate-based permission restrictions, or not affected by the version range are not vulnerable. SSVC confirms the attack is not automatable, further constraining realistic exploitation scenarios.
Impact	The CVSS 6.3 (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L) reflects a network-reachable flaw requiring low privileges - the attacker must possess valid first-factor credentials. Real-world risk is meaningfully lower than CVSS alone suggests: EPSS is 0.01% (3rd percentile), SSVC marks exploitation as none and automatable as no, there is no CISA KEV listing, and no public exploit code has been identified. The vulnerability is only exploitable on Go-based SSH servers that simultaneously implement MFA via PartialSuccessError AND rely on certificate-embedded Permissions for access control - a configuration intersection that narrows the exposed population considerably. The practical impact is integrity-focused: a user who should be constrained to a forced command could gain unconstrained shell access. Confidentiality and availability impacts are secondary. This is a real but niche risk, appropriately prioritized below critical or high-CVSS-but-widely-deployed issues.
Exploit ScenarioDerived	An attacker holds valid SSH credentials for an account whose SSH certificate carries a force-command restriction limiting them to a specific command (e.g., a restricted shell or backup script). The target server is a Go application using golang.org/x/crypto/ssh with MFA configured: the server's authentication callback returns PartialSuccessError with the certificate Permissions on first-factor success. Because those Permissions are silently dropped, after the attacker completes the second factor, they receive an unrestricted shell session rather than the constrained one their certificate mandated. No public exploit code identified at time of analysis, but the attack is conceptually straightforward given knowledge of the MFA flow.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Jun 02, 2026

SSH certificate permission enforcement in golang.org/x/crypto/ssh fails silently during multi-factor authentication flows, allowing authenticated users to bypass certificate-enforced restrictions such as force-command. Specifically, when an SSH server authentication callback returns PartialSuccessError with non-nil Permissions (as occurs in MFA sequences where a first factor succeeds and a second is required), those certificate permissions are silently discarded rather than propagated to the final session. Any Go-based SSH server using this library with both MFA and certificate-based permission restrictions is affected in versions prior to 0.52.0. No public exploit identified at time of analysis, and CISA KEV does not list this vulnerability.

RemediationAI

Upgrade golang.org/x/crypto to version 0.52.0 or later, which resolves the silent permission discard by returning a connection error when non-nil Permissions are passed with PartialSuccessError - see the upstream change at go.dev/cl/781621 and the Go vulnerability database entry at pkg.go.dev/vuln/GO-2026-5014. The fix is a breaking behavioral change: server implementations that previously returned non-nil Permissions alongside PartialSuccessError will now see connections fail, requiring code review of custom authentication callbacks. If immediate patching is not feasible, a compensating control is to audit all SSH server authentication callback implementations and ensure PartialSuccessError is returned with nil Permissions, deferring permission assignment to the final successful authentication stage - note this workaround requires code changes and careful testing to avoid introducing logic errors in permission assignment. Do not rely on network-layer filtering alone, as the vulnerability is exploitable by users who already hold valid first-factor credentials.

Affected VersionsENISA

golang.org/x/crypto/ssh 0 <0.52.0

Affected Packages

go golang.org/x/crypto fix: 0.52.0

go golang.org/x/crypto/ssh fix: 0.52.0

euvd golang_org_x_crypto_ssh fix: 0.52.0

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 3 packages in go, euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The affected component is golang.org/x/crypto/ssh (CPE: cpe:2.3:a:golang.org/x/crypto:golang.org/x/crypto/ssh:*:*:*:*:*:*:*:*), Go's extended cryptography library providing SSH protocol support. The SSH certificate model allows embedding permissions and extensions - such as force-command, which constrains the commands an authenticated user may execute - directly into certificates. In multi-factor authentication implementations, the PartialSuccessError type signals to the SSH handshake engine that the first authentication factor succeeded and a second is required. The bug (CWE-295: Improper Certificate Validation) is that the handshake engine silently discards the Permissions struct carried in a PartialSuccessError return value rather than propagating it into the final authenticated session context. The fix, introduced in 0.52.0, converts this silent discard into a connection error, forcing implementers to handle the condition correctly. The issue is tracked at go.dev/issue/79562 and announced via golang-announce.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (Go) PRIMARY 6.3 MEDIUM

AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

SUSE MEDIUM

Red Hat 8.8 HIGH

Primary rating from Vendor (Go).

CVSS VectorVendor: Go

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

Low

Lifecycle Timeline

CVSS changed

Jun 02, 2026 - 16:37 NVD

6.3 (None) 6.3 (MEDIUM)

Patch available

May 22, 2026 - 04:31 EUVD

CVE Published

May 22, 2026 - 02:31 nvd

UNKNOWN (no severity yet)

DescriptionCVE.org

When an SSH server authentication callback returned PartialSuccessError with non-nil Permissions, those permissions were silently discarded, potentially dropping certificate restrictions such as force-command after a second factor succeeded. Returning non-nil Permissions with PartialSuccessError now results in a connection error.

Threat Intelligence Overview

EPSS Score

0.0%

Top 97% exploitable

Threat Intel

1 sources

Exploit

POC

Public exploit code exists

Data Quality

8 sources

Confidence: High

EUVD

NVD

CVE.org

EPSS

Vulnrichment GHSA MSRC Vendor

GitHub

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC Yes

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation

None

System Exposure· derived

Open

Automatable

Human Impact· derived

Medium

Technical Impact

Partial

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +32

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Related Vulnerabilities in golang.org/x/crypto SSH Implementation Vulnerabilities

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Same weakness CWE-295 – Improper Certificate Validation

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Vendor StatusVendor

SUSE

Severity: Medium

Product	Status
openSUSE Leap 16.0	Fixed
openSUSE Tumbleweed	Fixed
SUSE Linux Enterprise Module for HPC 15 SP7	Affected
SUSE Linux Enterprise High Performance Computing 15 SP7	Affected
SUSE Linux Enterprise Server 15 SP6-LTSS	Affected

References

Advisories & patches

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