CVE-2026-39831
Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh
Description
The Verify() method for FIDO/U2F security key types ([email protected], [email protected]) 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.
INFO
Published Date :
May 22, 2026, 4:16 a.m.
Last Modified :
June 2, 2026, 4:33 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
Solution
- Implement user presence check for FIDO/U2F keys.
- Return "no-touch-required" extension in PublicKeyCallback.
- Ensure signatures require physical user touch.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-39831.
| URL | Resource |
|---|---|
| https://go.dev/cl/781662 | Issue Tracking |
| https://go.dev/issue/79566 | Issue Tracking |
| https://groups.google.com/g/golang-announce/c/a082jnz-LvI | Mailing List |
| https://pkg.go.dev/vuln/GO-2026-5019 | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-39831 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-39831
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-39831 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-39831 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jun. 02, 2026
Action Type Old Value New Value Added CWE CWE-862 Added CPE Configuration OR *cpe:2.3:a:golang:crypto:*:*:*:*:*:go:*:* versions up to (excluding) 0.52.0 Added Reference Type Go Project: https://go.dev/cl/781662 Types: Issue Tracking Added Reference Type Go Project: https://go.dev/issue/79566 Types: Issue Tracking Added Reference Type Go Project: https://groups.google.com/g/golang-announce/c/a082jnz-LvI Types: Mailing List Added Reference Type Go Project: https://pkg.go.dev/vuln/GO-2026-5019 Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
May. 22, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N -
New CVE Received by [email protected]
May. 22, 2026
Action Type Old Value New Value Added Description The Verify() method for FIDO/U2F security key types ([email protected], [email protected]) 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. Added Reference https://go.dev/cl/781662 Added Reference https://go.dev/issue/79566 Added Reference https://groups.google.com/g/golang-announce/c/a082jnz-LvI Added Reference https://pkg.go.dev/vuln/GO-2026-5019