CVE-2026-39834

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
golang-go.crypto	26.10 stonking	Not affected
	26.04 LTS resolute	Fixed in 1:0.47.0-1ubuntu0.1~esm1
	25.10 questing	Ignored end of life, was needed
	24.04 LTS noble	Fixed in 1:0.19.0-1ubuntu0.1~esm2
	22.04 LTS jammy	Fixed in 1:0.0~git20211202.5770296-1ubuntu0.1~esm2
	20.04 LTS focal	Fixed in 1:0.0~git20200221.2aa609c-1ubuntu0.1~esm2
	18.04 LTS bionic	Fixed in 1:0.0~git20170629.0.5ef0053-2ubuntu0.1~esm2
	16.04 LTS xenial	Fixed in 1:0.0~git20151201.0.7b85b09-2ubuntu0.1~esm2
snapd	26.10 stonking	Needs evaluation
	26.04 LTS resolute	Needs evaluation
	25.10 questing	Ignored end of life, was needs-triage
	24.04 LTS noble	Needs evaluation
	22.04 LTS jammy	Needs evaluation
	20.04 LTS focal	Needs evaluation
	18.04 LTS bionic	Needs evaluation
	16.04 LTS xenial	Needs evaluation
lxd	26.10 stonking	Not in release
	26.04 LTS resolute	Not in release
	25.10 questing	Not in release
	24.04 LTS noble	Not in release
	22.04 LTS jammy	Not in release
	20.04 LTS focal	Not affected
	18.04 LTS bionic	Fixed in 3.0.3-0ubuntu1~18.04.2+esm3
	16.04 LTS xenial	Fixed in 2.0.11-0ubuntu1~16.04.4+esm3
google-guest-agent	26.10 stonking	Not affected
	26.04 LTS resolute	Fixed in 20250506.01-0ubuntu2.1
	25.10 questing	Fixed in 20250506.01-0ubuntu1.2
	24.04 LTS noble	Fixed in 20250116.00-0ubuntu1~24.04.4
	22.04 LTS jammy	Fixed in 20250116.00-0ubuntu1~22.04.3
	20.04 LTS focal	Fixed in 20250116.00-0ubuntu1~20.04.0+esm3
	18.04 LTS bionic	Fixed in 20241011.01-0ubuntu1~18.04.0+esm3
	16.04 LTS xenial	Fixed in 20240716.00-0ubuntu1~16.04.0+esm3

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Notes

jdstrand

snapd contains an embedded copy of golang-go.crypto lxd in 18.04 LTS and earlier contains an embedded copy of golang-go.crypto

hlibk

google-guest-agent contains an embedded copy of golang-go.crypto

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
golang-go.crypto	Upstream: e052873

Severity score breakdown

CVSS version: CVSS v3.0

Base score 9.1 · Critical

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality impact	None
Integrity impact	High
Availability impact	High

Scores

Parameter	Value
Base score	9.1 · Critical
Exploitability score	-
Impact score	-

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

References

Related Ubuntu Security Notices (USN)

USN-8447-2
LXD vulnerabilities
18 June 2026

USN-8447-3
Google Guest Agent vulnerabilities
22 June 2026