CVE-2026-39831: Golang.org/x/crypto FIDO/U2F Security Key Physical Presence Vulnerability

CRITICAL
Advisory Identifier: GHSA-89gr-r52h-f8rx
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CVSS 9.1
CWE-862
Published
Advisory Summary

CVE-2026-39831 is a CRITICAL (CVSS 9.1) fido/u2f security key physical presence vulnerability (CWE-862: Missing Authorization) affecting Golang.org/x/crypto libraries in the Go ecosystem. The issue involves fido/u2f security key physical presence check can be bypassed. Remediation is available by upgrading affected packages to version 0.52.0.

CVE-2026-39831 at a Glance

CVE Identifier CVE-2026-39831
GHSA Identifier GHSA-89gr-r52h-f8rx
Severity CRITICAL
CVSS v3.1 Base Score 9.1
CWE Classification CWE-862: Missing Authorization
Affected Product Golang.org/x/crypto
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 9.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-39831

To remediate this vulnerability, upgrade all affected Golang.org/x/crypto dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

golang.org/x/crypto fixed: 0.52.0 
Upgrade golang.org/x/crypto to 0.52.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for golang.org/x/crypto

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-39831, inspect your project dependencies for Golang.org/x/crypto:

inspect dependencies for golang.org/x/crypto

Analyze the terminal output to locate any version of Golang.org/x/crypto in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.52.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-862: Missing Authorization, where the product does not perform an authorization check when an actor attempts to access a resource or perform an action. In Golang.org/x/crypto, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

The Verify() method for FIDO/U2F security key types (sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519@openssh.com) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. To restore the previous behavior, return a "no-touch-required" extension in Permissions.Extensions from PublicKeyCallback.

CVE-2026-39831 Affected Golang.org/x/crypto Versions

1 component(s)
Fixed Versions:
0.52.0
Product / Package Ecosystem Affected Versions Fixed Version
golang.org/x/crypto
golang/golang.org/x/crypto
Go
< 0.52.0
0.52.0

References

NVD — CVE-2026-39831 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39831
cs.opensource.google/go/x/crypto PACKAGE
https://cs.opensource.google/go/x/crypto
go.dev/cl/781662 WEB
https://go.dev/cl/781662
go.dev/issue/79566 WEB
https://go.dev/issue/79566
groups.google.com/g/golang-announce/c... WEB
https://groups.google.com/g/golang-announce/c/a082jnz-LvI
pkg.go.dev/vuln/go-2026-5019 WEB
https://pkg.go.dev/vuln/GO-2026-5019

Frequently Asked Questions

What is CVE-2026-39831?
CVE-2026-39831 is a security vulnerability in Golang.org/x/crypto involving FIDO/U2F security key physical presence check can be bypassed under CWE-862: Missing Authorization.
Which Golang.org/x/crypto versions are affected?
Affected versions include releases prior to 0.52.0 across affected packages: golang.org/x/crypto.
What version fixes CVE-2026-39831?
Upgrading to 0.52.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is golang.org/x/crypto affected?
Yes, golang.org/x/crypto is affected in releases prior to 0.52.0. Upgrade your dependency to 0.52.0 or later.
What is the CVSS score of CVE-2026-39831?
CVE-2026-39831 has a CVSS v3.1 base score of 9.1 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-39831?
CVE-2026-39831 is classified under CWE-862: Missing Authorization (The product does not perform an authorization check when an actor attempts to access a resource or perform an action.).
How can I check Go dependencies for CVE-2026-39831?
Run the dependency tree command: 'inspect dependencies for golang.org/x/crypto'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-89gr-r52h-f8rx",
  "modified" : "2026-07-07T15:25:57Z",
  "published" : "2026-06-25T22:21:12Z",
  "aliases" : [ "CVE-2026-39831" ],
  "summary" : "golang.org/x/crypto: FIDO/U2F security key physical presence check can be bypassed",
  "details" : "The Verify() method for FIDO/U2F security key types (sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519@openssh.com) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. To restore the previous behavior, return a \"no-touch-required\" extension in Permissions.Extensions from PublicKeyCallback.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "golang.org/x/crypto"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.52.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-39831"
  }, {
    "type" : "PACKAGE",
    "url" : "https://cs.opensource.google/go/x/crypto"
  }, {
    "type" : "WEB",
    "url" : "https://go.dev/cl/781662"
  }, {
    "type" : "WEB",
    "url" : "https://go.dev/issue/79566"
  }, {
    "type" : "WEB",
    "url" : "https://groups.google.com/g/golang-announce/c/a082jnz-LvI"
  }, {
    "type" : "WEB",
    "url" : "https://pkg.go.dev/vuln/GO-2026-5019"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-862" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-25T22:21:12Z",
    "nvd_published_at" : "2026-05-22T04:16:22Z"
  }
}