Affected: golang.org/x/crypto/ssh/agent, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8.8 Telecommunications Update Service, Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions, Red Hat Enterprise Linux 9, Red Hat RHEM 1.0 for RHEL 9, Red Hat RHEM 1.1 for RHEL 10, Red Hat RHEM 1.1 for RHEL 9, Red Hat Cluster Observability Operator 1.5.0 and 38 more

When adding a key to a remote agent constraint extensions such as restrict-destination-v00@openssh.com were not serialized in the request. Destination restrictions were silently stripped when forwarding keys, allowing unrestricted use of the key on the remote host. The client now serializes all constraint extensions. Additionally, the in-memory keyring returned by NewKeyring() now rejects keys with unsupported constraint extensions instead of silently ignoring them.

Affected: Ubuntu:Pro:16.04:LTS: golang-go.crypto, Ubuntu:Pro:18.04:LTS: golang-go.crypto, Ubuntu:Pro:20.04:LTS: golang-go.crypto, Ubuntu:Pro:22.04:LTS: golang-go.crypto, Ubuntu:Pro:24.04:LTS: golang-go.crypto, Ubuntu:Pro:26.04:LTS: golang-go.crypto

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 1…