CVE-2026-39834
Published: May 22, 2026· Updated: May 28, 2026
Official 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.
Risk Analysis
This critical vulnerability in the golang:crypto package can lead to a denial of service when writing large amounts of data over an SSH channel. An integer overflow in the payload size calculation causes the write loop to spin indefinitely, sending empty packets. With a CVSS score of 9.1, this flaw can disrupt SSH communication and system availability.
No public exploit is currently known for this vulnerability. The flaw is remotely exploitable (AV:N) without requiring any authentication (PR:N) or user interaction (UI:N).
Update the golang:crypto package to a version that uses int64 for payload size calculations to prevent integer overflow. Ensure all applications using this package for SSH communication are updated.
Technical Analysis
CVE-2026-39834 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.
A successful exploit results in full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.1.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (4)
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-39834 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts