Google Guest Agent vulnerabilities

Summary

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 i Affected Ubuntu releases: 26.04, 25.10, 24.04, 22.04, 20.04, 18.04, 16.04. CVEs: CVE-2026-39831, CVE-2026-39834, CVE-2026-39830, CVE-2026-46595.