CVE-2026-39834 — x/crypto
CRITICALCVE-2026-39834 is a critical-severity (CVSS 9.1) CWE-190 vulnerability in golang.org/x/crypto. A fix is available for golang.org/x/crypto — see the affected versions and patch details below.
Invoking infinite loop on large channel writes 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.
- 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-2026-39834.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-39834 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 395,492 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
When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation.
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-2026-39834 is resolved across your whole dependency graph.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
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 |
|---|---|---|
| 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 |
| multicluster engine for Kubernetes 2.11 | multicluster-engine/hypershift-addon-rhel9-operator:1786912006 | RHSA-2026:57194 |
| OpenShift API for Data Protection 1.6 | oadp/oadp-velero-rhel9:1784058822 | RHSA-2026:43692 |
| Red Hat Hardened Images | golang1-26-main-1.26.8-0.1.hum1 | RHSA-2026:62391 |
| Red Hat Hardened Images | golang1-27-main-1.27.1-0.1.hum1 | RHSA-2026:66561 |
| Red Hat Openshift Data Foundation 4.22 | odf4/cephcsi-rhel9:1782932114 | RHSA-2026:37387 |
Frequently Asked Questions
Is CVE-2026-39834 in your dependencies?
Find it across Go, including transitive dependencies.