What is the CVSS score of EUVD-2026-31398?

EUVD-2026-31398 has a CVSS 3.1 base score of 10.0 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L. EPSS exploitation probability: 0.0%.

How to fix or mitigate EUVD-2026-31398?

Within 24 hours: Conduct inventory of all Go applications using golang.org/x/crypto/ssh (check go.mod, go.sum, and vendor directories); prioritize SSH services with callback-based authentication. Within 7 days: Update golang.org/x/crypto/ssh to version 0.52.0, rebuild affected applications, and deploy across production. Within 30 days: Audit SSH access logs and verify source-address restrictions are properly enforced post-patch.

golang.org/x/crypto/ssh EUVD-2026-31398

Q: Which versions of golang.org/x/crypto/ssh are affected by EUVD-2026-31398?

An authorization bypass in the Go SSH library (golang.org/x/crypto/ssh) enables remote attackers to circumvent source-address restrictions, a critical network control limiting SSH access to…. A patch is available.

| CVE-2026-46595 CRITICAL

Incorrect Authorization (CWE-863)

2026-05-22 Go

GHSA-x527-x647-q7gg

Authentication Bypass Golang Org X Crypto Ssh Golang Org X Crypto

10.0

CVSS 3.1 · Vendor: Go

View

Attack ChainAIDerived

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

Access

Identify Go-based SSH server using non-pubkey auth
Delivery

Obtain valid credentials for a restricted account
Exploit

Connect from disallowed source IP
Execution

Source-address check skipped due to callback type
Impact

Authenticate and gain shell from unauthorized network location

Vulnerability Assessment

Weakness	CWE CWE-863 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V8 - Authorization Authorization logic validation MITRE ATT&CK 1 technique across 1 tactic: Privilege Escalation The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Exploitation Conditions	Exploitation requires that the target SSH server is built on golang.org/x/crypto/ssh prior to 0.52.0 AND is configured with a non-public-key authentication callback (PasswordCallback, KeyboardInteractiveCallback, GSSAPIWithMICConfig, or another non-PublicKeyCallback handler) AND relies on source-address restrictions (declared in certificates or authorized_keys-style options) as part of its authorization model. Limiting factors: the attacker must still pass the underlying authentication step (valid password, Kerberos ticket, etc.), so this is an authorization-control bypass rather than a pre-authentication remote-code-execution; servers that only use public-key authentication are not affected (CVE-2024-45337 already covered that path), and servers that do not use source-address pinning have nothing to bypass.
Impact	Signals are mixed and warrant careful interpretation. CVSS is reported as 10.0 with vector AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L, which implies unauthenticated network exploitation with scope change - however the actual weakness is a bypass of an authorization control (source-address checks) layered on top of normal SSH authentication, so the practical impact only materializes when a server (a) misuses non-public-key callbacks and (b) relies on source-address restrictions for security; the AV:N/PR:N rating is therefore plausible but the real-world exploitability is narrower than a raw 10.0 suggests. EPSS is 0.02% (4th percentile) and SSVC reports Exploitation: none, Automatable: yes, Technical Impact: partial, and there is no CISA KEV listing and no public exploit identified at time of analysis, which together indicate this is a latent risk rather than an active threat. The Automatable: yes signal does mean that once a target is identified, exploitation can be scripted, so operators of Go-based SSH servers that rely on source-address pinning should still prioritize patching.
Exploit ScenarioDerived	An attacker who has obtained valid credentials (for example a leaked password or a captured Kerberos ticket) for an account on a Go-based SSH server attempts to authenticate from an IP address outside the source-address allowlist that the operator believed was enforced. Because the server is configured with a PasswordCallback or KeyboardInteractiveCallback rather than PublicKeyCallback, the source-address validation is silently skipped and the login succeeds, granting the attacker access from an unapproved network location. No public exploit is identified at time of analysis, but the bug is straightforward to trigger once valid credentials and a misconfigured target are in hand.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – May 28, 2026

Authorization bypass in the Go golang.org/x/crypto/ssh package before version 0.52.0 allows remote attackers to circumvent source-address restrictions when SSH server configurations use callback authentication types other than public key. This is an incomplete-fix follow-up to CVE-2024-45337, which only addressed the public-key callback path while leaving other callback types vulnerable to the same source-address validation skip. No public exploit identified at time of analysis, EPSS is very low at 0.02%, and SSVC indicates no observed exploitation though the issue is automatable with partial technical impact.

RemediationAI

Upgrade golang.org/x/crypto to version 0.52.0 or later (vendor-released patch: 0.52.0) by running go get golang.org/x/crypto@v0.52.0 and rebuilding all affected binaries, since this is a compile-time dependency rather than a runtime library. The fix commit is https://go.dev/cl/781642 and the Go vulnerability advisory is https://pkg.go.dev/vuln/GO-2026-5023; consult the golang-announce notice at https://groups.google.com/g/golang-announce/c/a082jnz-LvI for the full disclosure. If immediate upgrade is not possible, the practical workaround is to stop relying on SSH source-address restrictions as a security boundary when using password, keyboard-interactive, or GSSAPI callbacks - instead enforce IP allowlisting at the network layer via firewall rules or a reverse proxy, accepting the operational trade-off of duplicating policy outside the SSH server configuration; alternatively, restrict server configurations to PublicKeyCallback only, which prevents the bypass but breaks any deployment that requires password or interactive auth.

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 golang.org/x/crypto/ssh package is the canonical Go implementation of the SSH protocol used widely by Go-based servers, bastions, and CI/CD tooling. The vulnerability is a CWE-863 incorrect authorization weakness in the server-side authentication callback handling: when an SSH server configuration registers authentication callbacks of a type other than PublicKeyCallback (for example PasswordCallback, KeyboardInteractiveCallback, or GSSAPIWithMICConfig), the source-address restriction logic - which is meant to enforce per-principal IP allowlists declared in certificates or authorized_keys options - is bypassed entirely. CVE-2024-45337 closed this gap only for public-key flows, and CVE-2026-46595 extends the same fix to the remaining callback types. The affected CPE is cpe:2.3:a:golang.org/x/crypto:golang.org/x/crypto/ssh, and the fix landed via go.dev/cl/781642 and is tracked as GO-2026-5023.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (Go) PRIMARY 10.0 CRITICAL

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

SUSE 8.1 HIGH

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

Red Hat 7.1 HIGH

Primary rating from Vendor (Go).

CVSS VectorVendor: Go

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

Low

Lifecycle Timeline

CVSS changed

May 28, 2026 - 15:07 NVD

10.0 (None) 10.0 (CRITICAL)

Patch available

May 22, 2026 - 04:31 EUVD

CVE Published

May 22, 2026 - 02:31 nvd

UNKNOWN (no severity yet)

DescriptionCVE.org

Previously, CVE-2024-45337 fixed an authorization bypass for misused ssh server configurations; if any other type of callback is passed other than public key, then the source-address validation would be skipped.

Executive ViewAI

Why It Matters

An authorization bypass in the Go SSH library (golang.org/x/crypto/ssh) enables remote attackers to circumvent source-address restrictions, a critical network control limiting SSH access to authorized locations. Organizations using Go-based SSH services with callback-based authentication are vulnerable to unauthorized access from unexpected network sources. This is a regression from a previously attempted fix, requiring immediate patching to restore security control effectiveness.

Business Impact: Severe

Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score

0.0%

Top 96% exploitable

Threat Intel

1 sources

Social Media

Sightings

Data Quality

7 sources

Confidence: High

EUVD

NVD

CVE.org

EPSS

Vulnrichment GHSA MSRC Vendor CIRCL

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 CRITICAL

CISA KEV No

Public POC No

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

CRITICAL severity

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.