Medium [CVE-2026-59998] Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory
This medium-severity Red Hat Linux advisory covers CVE-2026-59998 affecting Red Hat Hardened Images, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6.
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Summary
sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAcceptorCheck has no value if the server is in Windows Active Directory. A flaw was found in OpenSSH.
This could lead to unintended information disclosure and impact data integrity. Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N).
Weakness: CWE-909. Affected Red Hat products: Red Hat Hardened Images; Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat OpenShift Container Platform 4.
Red Hat fixing advisory: RHSA-2026:37382.
Affected products named by the advisory: Red Hat package: openssh.
- < 10.4
Official advisory · high-confidence parse· fetched 3 hours ago·verify at source
- openssh-main-10.4p1-1.hum1
- RHSA-2026:37382
Official advisory · high-confidence parse· fetched 3 hours ago·verify at source
Mitigation checklist
- To mitigate this issue, avoid using GSSAPI authentication for `sshd` when the server is integrated with a Windows Active Directory environment. If GSSAPI authentication is not strictly required, it can be disabled by setting `GSSAPIAuthentication no` in the `/etc/ssh/sshd_config` file. After modifying the configuration, the `sshd` service must be restarted for the changes to take effect. Note that restarting the `sshd` service will terminate all active SSH sessions. ```bash # echo "GSSAPIAuthentication no" >> /etc/ssh/sshd_config # systemctl restart sshd ``` Alternatively, if GSSAPI authentication is necessary in such an environment, ensure that the network path between the client and the `sshd` server, and to the Active Directory, is secured and trusted to prevent man-in-the-middle attacks.
Official advisory · high-confidence parse· fetched 3 hours ago·verify at source
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