========================================================================== Ubuntu Security Notice USN-8447-3 June 22, 2026
google-guest-agent vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 26.04 LTS
- Ubuntu 25.10
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
Summary:
Several security issues were fixed in Google Guest Agent.
Software Description:
- google-guest-agent: Google Compute Engine Guest Agent
Details:
USN-8447-1 fixed vulnerabilities in Go Cryptography. This update provides
the corresponding updates for Go Cryptography code embedded in Google
Guest Agent.
Original advisory details:
It was discovered that Go Cryptography did not properly handle SSH global
request responses. A remote attacker could possibly use this issue to cause
a denial of service. (CVE-2026-39830)
It was discovered that Go Cryptography did not properly verify user
presence when using FIDO/U2F security keys. An attacker could possibly use
this issue to bypass user presence verification for hardware security keys.
This issue only affected Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04
LTS, and Ubuntu 26.04 LTS. (CVE-2026-39831)
It was discovered that Go Cryptography did not properly serialize SSH agent
key constraint extensions. An attacker could possibly use this issue to
bypass intended key usage restrictions. This issue only affected Ubuntu
20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS.
(CVE-2026-39832)
It was discovered that Go Cryptography did not properly enforce the
confirm-before-use constraint in the SSH agent keyring. An attacker could
possibly use this issue to use SSH keys without the required user
confirmation. (CVE-2026-39833)
It was discovered that Go Cryptography had an integer overflow when
handling large SSH channel writes. A remote attacker could possibly use
this issue to cause a denial of service. (CVE-2026-39834)
It was discovered that Go Cryptography did not properly check certificate
authority key revocation. An attacker could possibly use this issue to
bypass certificate authority revocation checks. This issue only affected
Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and
Ubuntu 26.04 LTS. (CVE-2026-42508)
It was discovered that Go Cryptography did not properly enforce the source-
address critical option for all SSH server callback types. An attacker
could possibly use this issue to bypass source address authorization
restrictions. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-46595)
Update instructions:
The problem can be corrected by updating your system to the following
package versions:
Ubuntu 26.04 LTS
google-guest-agent 20250506.01-0ubuntu2.1
Ubuntu 25.10
google-guest-agent 20250506.01-0ubuntu1.2
Ubuntu 24.04 LTS
google-guest-agent 20250116.00-0ubuntu1~24.04.4
Ubuntu 22.04 LTS
google-guest-agent 20250116.00-0ubuntu1~22.04.3
Ubuntu 20.04 LTS
google-guest-agent 20250116.00-0ubuntu1~20.04.0+esm3
Available with Ubuntu Pro
Ubuntu 18.04 LTS
google-guest-agent 20241011.01-0ubuntu1~18.04.0+esm3
Available with Ubuntu Pro
Ubuntu 16.04 LTS
google-guest-agent 20240716.00-0ubuntu1~16.04.0+esm3
Available with Ubuntu Pro
In general, a standard system update will make all the necessary changes.
References:
https://ubuntu.com/security/notices/USN-8447-3
https://ubuntu.com/security/notices/USN-8447-2
https://ubuntu.com/security/notices/USN-8447-1
CVE-2026-39830, CVE-2026-39831, CVE-2026-39834, CVE-2026-46595
Package Information:
https://launchpad.net/ubuntu/+source/google-guest-agent/20250506.01-0ubuntu2.1
https://launchpad.net/ubuntu/+source/google-guest-agent/20250506.01-0ubuntu1.2
https://launchpad.net/ubuntu/+source/google-guest-agent/20250116.00-0ubuntu1~24.04.4
https://launchpad.net/ubuntu/+source/google-guest-agent/20250116.00-0ubuntu1~22.04.3
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