CVE-2026-39834
Analyzed Analyzed - Analysis Complete
Integer Overflow in Go SSH Channel Write Handling

Publication date: 2026-05-22

Last updated on: 2026-05-28

Assigner: Go Project

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.
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Meta Information
Published
2026-05-22
Last Modified
2026-05-28
Generated
2026-06-11
AI Q&A
2026-05-23
EPSS Evaluated
2026-06-10
NVD
CVE-2026-39834
EUVD
EUVD-2026-31400
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
golang crypto to 0.52.0 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-190 The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.
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Compliance Impact

The provided information does not specify any direct impact of CVE-2026-39834 on compliance with common standards and regulations such as GDPR or HIPAA.

Executive Summary

This vulnerability occurs in the Go programming language's SSH implementation when writing data larger than 4GB in a single Write call on an SSH channel.

An integer overflow happens in the internal payload size calculation, causing the write loop to spin indefinitely. Instead of progressing, it sends empty packets repeatedly.

The issue was fixed by changing the size comparison to use a 64-bit integer (int64) to prevent truncation and overflow.

Impact Analysis

This vulnerability can cause an SSH write operation to hang indefinitely when attempting to send data larger than 4GB in a single call.

As a result, the affected process may become unresponsive or stuck in an infinite loop, sending empty packets without making progress.

This can lead to denial of service conditions or degraded performance in applications relying on the affected SSH implementation.

Mitigation Strategies

To mitigate this vulnerability, you should update the golang.org/x/crypto package to version v0.52.0 or later, where the issue has been fixed by changing the size comparison to use int64 to prevent truncation.

Ensure that any applications using the affected SSH functions such as Dial, NewClientConn, NewServerConn, and various Session methods (CombinedOutput, Output, Run, Shell, Start) are rebuilt and redeployed with the updated package.

Detection Guidance

This vulnerability causes an infinite loop when writing data larger than 4GB in a single Write call on an SSH channel, resulting in the write loop spinning indefinitely and sending empty packets without making progress.

Detection could involve monitoring SSH channel traffic for unusual behavior such as continuous empty packets being sent without progress during large data transfers.

Since the issue is specific to the golang.org/x/crypto SSH implementation before version v0.52.0, checking the version of the Go SSH package in use is a primary step.

No specific commands or network detection tools are provided in the available resources.

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