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CVE Record

CVE-2026-39828: Invoking bypass of certificate restrictions in golang.org/x/crypto/ssh

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.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This flaw affects Go applications that use golang.org/x/crypto/ssh as an SSH server with SSH certificates and multi-factor authentication. In a specific authentication path, certificate restrictions could be dropped after a second factor succeeds, potentially allowing broader access than intended.

Executive priority

Prioritize systems where SSH certificate restrictions protect privileged actions, automation accounts, or constrained administrative access. Treat internet-reachable or partner-facing custom SSH services as higher urgency. Internal-only systems still matter if certificate restrictions enforce separation of duties.

Technical view

If an SSH server authentication callback returned PartialSuccessError with non-nil Permissions, those permissions were silently discarded. That could remove certificate restrictions such as force-command after subsequent authentication completed. The Go fix changes this case to fail the connection instead of continuing with lost permissions.

Likely exposure

Exposure is most likely in custom Go SSH servers or products embedding golang.org/x/crypto/ssh that use certificate-based restrictions plus multi-factor or partial authentication flows. Standard OpenSSH deployments are not indicated by the provided sources.

Exploitation context

The source bundle does not show known active exploitation, and KEV is false. Exploitation would require a reachable affected SSH server and an authentication flow that returns PartialSuccessError with permissions attached. The practical risk depends heavily on application-specific callback logic.

Researcher notes

The evidence supports an authorization bypass in a specific x/crypto/ssh server authentication state transition. The bundle does not provide a complete affected version range beyond the package identifier, so confirm with GO-2026-5014, the Go change, and downstream vendor advisories.

Mitigation direction

  • Update golang.org/x/crypto/ssh according to GO-2026-5014 and vendor guidance.
  • Apply relevant Red Hat advisories for packaged affected components.
  • Audit SSH authentication callbacks for PartialSuccessError with non-nil Permissions.
  • Review certificate restriction enforcement for force-command and similar controls.

Validation and detection

  • Inventory Go applications importing golang.org/x/crypto/ssh.
  • Check dependency manifests and build artifacts for affected x/crypto versions.
  • Review server authentication callback code for partial-success handling.
  • Confirm certificate restrictions remain enforced after multi-factor authentication.
  • Track GO-2026-5014 and Red Hat errata for fixed package status.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-281: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · medium confidence lookup

CWE-863: Authorization and privilege behavior lookup

Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-39828 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
32Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9redhat-SADP
6.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L2.83.4CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

8.8High
CVSS 3.1 vector shape for CVE-2026-39828Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPgolang.org/x/crypto/ssh: golang.org/x/crypto/ssh: Unauthorized command execution via discarded SSH permissions
other:Red Hat severity ratingcvssV3_1
  • 2026-05-22T04:01:46.775Z: Reported to Red Hat.
  • 2026-05-22T02:31:26.883Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
golang.org/x/cryptogolang.org/x/crypto/sshgolang.org/x/crypto/ssh, 0unaffected
Weakness

CWE details

CWE-281CWE-863

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-281 · source CWE mapping

Improper Preservation of Permissions

Improper Preservation of Permissions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-863 · source CWE mapping

Incorrect Authorization

Incorrect Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs