CVE-2026-39831 (GCVE-0-2026-39831)
Vulnerability from cvelistv5
Published
2026-05-22 02:31
Modified
2026-05-22 18:52
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| golang.org/x/crypto | golang.org/x/crypto/ssh |
Version: 0 ≤ |
{
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"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 9.1,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
"version": "3.1"
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"id": "CVE-2026-39831",
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{
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"role": "CISA Coordinator",
"timestamp": "2026-05-22T18:51:41.233749Z",
"version": "2.0.3"
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"providerMetadata": {
"dateUpdated": "2026-05-22T18:52:08.344Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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"title": "CISA ADP Vulnrichment"
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"cna": {
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{
"collectionURL": "https://pkg.go.dev",
"defaultStatus": "unaffected",
"packageName": "golang.org/x/crypto/ssh",
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"programRoutines": [
{
"name": "CertChecker.CheckCert"
},
{
"name": "skECDSAPublicKey.Verify"
},
{
"name": "skEd25519PublicKey.Verify"
},
{
"name": "connection.serverAuthenticate"
},
{
"name": "CertChecker.Authenticate"
},
{
"name": "CertChecker.CheckHostKey"
},
{
"name": "Certificate.Verify"
},
{
"name": "Dial"
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{
"name": "NewClientConn"
},
{
"name": "NewServerConn"
}
],
"vendor": "golang.org/x/crypto",
"versions": [
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"lessThan": "0.52.0",
"status": "affected",
"version": "0",
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"credits": [
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"value": "NCC Group Cryptography Services, sponsored by Teleport"
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}
],
"problemTypes": [
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"descriptions": [
{
"description": "CWE-290: Authentication Bypass by Spoofing",
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"providerMetadata": {
"dateUpdated": "2026-05-22T02:31:27.436Z",
"orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
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"references": [
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"url": "https://go.dev/issue/79566"
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{
"url": "https://groups.google.com/g/golang-announce/c/a082jnz-LvI"
},
{
"url": "https://go.dev/cl/781662"
},
{
"url": "https://pkg.go.dev/vuln/GO-2026-5019"
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"title": "Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh"
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"datePublished": "2026-05-22T02:31:27.436Z",
"dateReserved": "2026-04-07T18:13:03.528Z",
"dateUpdated": "2026-05-22T18:52:08.344Z",
"state": "PUBLISHED"
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"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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