What is the CVSS score of CVE-2026-39833?

CVE-2026-39833 has a contested CVSS base score of 9.1 from a third party (e.g. CISA-ADP), while the vendor rates it Critical. vuln.today uses the vendor rating as authoritative.

Is there a public PoC exploit available for CVE-2026-39833?

Yes, a public proof-of-concept exploit is available for CVE-2026-39833. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-39833?

Within 24 hours: Conduct inventory of all Go applications using golang.org/x/crypto/ssh/agent dependency and document current versions in use. Within 7 days: Upgrade golang.org/x/crypto/ssh/agent to version 0.52.0 or later in all affected applications, rebuild, and stage for production deployment. Within 30 days: Deploy all patched applications to production environments and validate SSH authentication workflows with confirmation prompts functioning correctly.

golang.org/x/crypto CVE-2026-39833

Q: Which versions of golang.org/x/crypto are affected by CVE-2026-39833?

Applications using Go's SSH agent library (golang.org/x/crypto/ssh/agent versions before 0.52.0) that implemented ConfirmBeforeUse controls to gate sensitive SSH key signing operations discover these…. A patch is available.

EUVD-2026-31389 CRITICAL

Missing Authorization (CWE-862)

2026-05-22 Go

GHSA-jppx-rxg9-jmrx

Authentication Bypass Golang Org X Crypto Ssh Agent Golang Org X Crypto

Critical

Disputed · 9.1 Vendor: Go

View

Attack ChainAIDerived

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

Access

Reach exposed SSH agent socket
Delivery

Enumerate loaded keys with ConfirmBeforeUse constraint
Exploit

Send sign request to in-memory keyring
Execution

Receive signature without confirmation prompt
Impact

Authenticate to downstream SSH server as victim

Vulnerability Assessment

Weakness	CWE CWE-862 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V8 - Authorization Authorization checks on every request 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 application uses the in-memory keyring constructor agent.NewKeyring() from golang.org/x/crypto/ssh/agent prior to 0.52.0, that at least one key has been added with the ConfirmBeforeUse constraint as a security control the application relies on, and that the attacker has a path to issue sign requests against that keyring (typically via the SSH agent protocol over a socket or forwarded channel that the embedding program exposes). Limiting factors: applications that never set ConfirmBeforeUse, do not import this package, or expose the agent only to a fully trusted local user are not exploitable in any meaningful sense; the CVSS AV:N rating is realized only when the embedding application surfaces the agent to a network-reachable attacker, which is a deployment choice rather than a default.
Impact	The signals here conflict in a way that defenders should reconcile carefully. CVSS 9.1 (AV:N/AC:L/PR:N/UI:N, C:H/I:H) reflects the worst-case where an attacker can reach the agent over the network and obtain arbitrary signatures, and SSVC marks technical impact 'total' and automatable 'yes' - both alarming. However, EPSS is 0.02% (5th percentile), the vulnerability is not in CISA KEV, SSVC exploitation is 'none', and the bug only matters for applications that (a) embed this keyring and (b) actually rely on ConfirmBeforeUse as a security control - a niche deployment shape. The CVSS network vector also assumes the agent is reachable to an attacker, which depends entirely on how the embedding application exposes it; many ssh-agent deployments are local-socket only. Net assessment: high-severity-but-narrow-applicability - prioritize patching where the keyring is exposed or where ConfirmBeforeUse was treated as a real authorization gate, otherwise standard patch cadence is reasonable.
Exploit ScenarioDerived	An attacker who can reach an SSH agent built on this keyring (for example, via a forwarded agent socket or an agent exposed over a network channel by the embedding application) requests a signature using a key that the legitimate user had loaded with ConfirmBeforeUse expecting an interactive prompt; the keyring silently returns the signature without any user interaction. The attacker uses that signature to authenticate to downstream SSH servers as the user. No public exploit is identified at time of analysis, and exploitation requires the victim application to actually use this specific package and constraint.

Act Now Prioritize within 24-48h. Why: CRITICAL severity + public POC available.

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – May 28, 2026

Authentication bypass in Go's golang.org/x/crypto/ssh/agent in-memory keyring (versions before 0.52.0) allows SSH key signing operations to proceed without the intended ConfirmBeforeUse user confirmation prompt. Applications that relied on this constraint to gate sensitive signing actions effectively had no protection, with no error returned to indicate the constraint was silently ignored. No public exploit identified at time of analysis and EPSS is very low (0.02%), but SSVC rates technical impact as total.

RemediationAI

Vendor-released patch: upgrade golang.org/x/crypto to 0.52.0 or later (run 'go get golang.org/x/crypto@v0.52.0' and rebuild affected binaries), tracked in the upstream issue at https://go.dev/issue/79436 with fixes in https://go.dev/cl/778640 and https://go.dev/cl/778641 and announced at https://groups.google.com/g/golang-announce/c/a082jnz-LvI. After upgrading, NewKeyring() now returns an error when an unsupported constraint such as ConfirmBeforeUse is requested, so audit calling code to handle that error and either implement confirmation out-of-band or refuse to add the key. Until the upgrade can be deployed, do not rely on ConfirmBeforeUse as a security boundary in the in-memory keyring - instead remove keys requiring confirmation from the keyring, gate signing in the calling application layer, or restrict agent socket exposure to trusted local processes only; the trade-off is loss of per-use confirmation UX that some workflows depend on.

Affected VersionsENISA

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

Affected Packages

go golang.org/x/crypto fix: 0.52.0

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

euvd golang_org_x_crypto_ssh_agent 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 vulnerability lives in the agent.NewKeyring() implementation of the golang.org/x/crypto/ssh/agent package, which provides an in-memory SSH agent keyring used by Go programs that implement or embed an ssh-agent. SSH agent key constraints (RFC 4251 / draft-miller-ssh-agent) allow callers to attach restrictions to a key such as ConfirmBeforeUse, which is supposed to require an out-of-band confirmation before each signing operation. The CPE confirms the affected component is cpe:2.3:a:golang.org/x/crypto:golang.org/x/crypto/ssh/agent. CWE-862 (Missing Authorization) describes the root cause: the keyring accepted the constraint at AddKey time but the Sign path never consulted or enforced it, so the authorization check that callers expected was simply absent.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Sources disagree (Medium–Critical)

Vendor (Go) PRIMARY 9.1 CRITICAL

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

SUSE CRITICAL

Red Hat 5.5 MEDIUM

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: Go

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Lifecycle Timeline

CVSS changed

May 28, 2026 - 15:07 NVD

9.1 (None) 9.1 (CRITICAL)

Patch available

May 22, 2026 - 04:31 EUVD

CVE Published

May 22, 2026 - 02:31 nvd

UNKNOWN (no severity yet)

DescriptionCVE.org

The in-memory keyring returned by NewKeyring() silently accepted keys with the ConfirmBeforeUse constraint but never enforced it. The key would sign without any confirmation prompt, with no indication to the caller that the constraint was not in effect. NewKeyring() now returns an error when unsupported constraints are requested.

Executive ViewAI

Why It Matters

Applications using Go's SSH agent library (golang.org/x/crypto/ssh/agent versions before 0.52.0) that implemented ConfirmBeforeUse controls to gate sensitive SSH key signing operations discover these protections are completely ineffective, silently bypassed with no error indication. Organizations relying on user-confirmation-based SSH security controls face the risk that their intended access gates are non-functional, potentially allowing unauthorized key operations without audit trails or operator awareness. This affects all Go-based systems where administrators configured confirmation requirements expecting them to be enforced.

Business Impact: High

Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score

0.0%

Top 95% exploitable

Threat Intel

1 sources

Exploit

POC

Public exploit code exists

Social Media

Sightings

Data Quality

7 sources

Confidence: High

EUVD

NVD

CVE.org

EPSS

Vulnrichment GHSA MSRC Vendor CIRCL

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 CRITICAL

CISA KEV No

Public POC Yes

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

CRITICAL severity + public POC available

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.