How severe is CVE-2026-39834?

CVE-2026-39834 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.

Is CVE-2026-39834 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-39834?

CVE-2026-39834 affects Golang Crypto. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-39834?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-39834 have an EU (EUVD) identifier?

Yes. CVE-2026-39834 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-31400.

When was CVE-2026-39834 published?

CVE-2026-39834 was published on 2026-05-22 and last updated on 2026-06-17.

CVE-2026-39834

CVE-2026-39834 is a critical-severity vulnerability in Golang Crypto with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-190.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 0% (37th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-31400
Weakness: CWE-190
Affected product: Golang Crypto
Published: 2026-05-22
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-39834?: 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.
How severe is CVE-2026-39834?: CVE-2026-39834 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.
Is CVE-2026-39834 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39834?: CVE-2026-39834 affects Golang Crypto. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-39834?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-39834 have an EU (EUVD) identifier?: Yes. CVE-2026-39834 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-31400.
When was CVE-2026-39834 published?: CVE-2026-39834 was published on 2026-05-22 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:golang:crypto:*:*:*:*:*:go:*:*

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