CVE-2026-39831 — x/crypto
CRITICALCVE-2026-39831 is a critical-severity (CVSS 9.1) CWE-862 vulnerability in golang.org/x/crypto. A fix is available for golang.org/x/crypto — see the affected versions and patch details below.
Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-39831.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-39831 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
golang.org/x/cryptoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | golang.org/x/crypto | all versions | 0.52.0go get golang.org/x/crypto@v0.52.0 |
Affected Products
cryptogolangDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for golang.org/x/crypto, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update golang.org/x/crypto to 0.52.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39831 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 9.6 Extended Update Support | podman-5:5.4.0-22.el9_6.5 | RHSA-2026:67450 |
| RHEM 1.1 for RHEL 10 | flightctl-0:1.1.4-1.el10em | RHSA-2026:68334 |
| Cert Manager support for Red Hat OpenShift release 1.17 | cert-manager/jetstack-cert-manager-acmesolver-rhel9:1791371080 | RHSA-2026:82304 |
| Cert Manager support for Red Hat OpenShift release 1.17 | cert-manager/cert-manager-operator-rhel9:1791788287 | RHSA-2026:82322 |
| Cluster Observability Operator 1.5.3 | cluster-observability-operator/cluster-observability-rhel9-operator:1787593637 | RHSA-2026:61314 |
| Logging Subsystem for Red Hat OpenShift 6.5 | openshift-logging/cluster-logging-rhel9-operator:1789659166 | RHSA-2026:70870 |
| Logging Subsystem for Red Hat OpenShift 6.6 | openshift-logging/cluster-logging-rhel9-operator:1788439505 | RHSA-2026:66521 |
| multicluster engine for Kubernetes 2.10 | multicluster-engine/hypershift-addon-rhel9-operator:1786548381 | RHSA-2026:54432 |
Frequently Asked Questions
Is CVE-2026-39831 in your dependencies?
Find it across Go, including transitive dependencies.