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 :
May 22, 2026, 4:16 a.m.
Remotely Exploit :
No
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-39831
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
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 | |
| https://go.dev/issue/79566 | |
| https://groups.google.com/g/golang-announce/c/a082jnz-LvI | |
| https://pkg.go.dev/vuln/GO-2026-5019 |
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.
-
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