CVE-2026-59998: sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAcceptorCheck has no value if the server is in Windows Active Directory.

mediumCVSS 4.8CVE-2026-59998

CSIRTS triage

vendor: OpenSSH product: OpenSSHOtheraffected: before 10.4

What: An undocumented security-relevant behavior in sshd affects GSSAPIStrictAcceptorCheck when the server is in Windows Active Directory.
Who is affected: Users of OpenSSH before version 10.4 are affected.
Urgency: Remediation is medium due to the medium severity of the vulnerability.
Action: Consider upgrading to OpenSSH version 10.4 or later.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 4.8
Published: 2026-07-02
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-59998

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-599980.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 8% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-59998	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

mediumCVE-2026-59998: sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAccept…nvd

Recent advisories for sshd in OpenSSH

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

mediumCVE-2026-60001: sshd in OpenSSH before 10.4 does not always honor the minimum authentication delay.nvd · 2026-07-08
lowCVE-2026-60000: sshd in OpenSSH before 10.4 allows remote attackers to cause a denial of service (resource con…nvd · 2026-07-08
mediumCVE-2026-59999: In sshd in OpenSSH before 10.4, DisableForwarding=yes was supposed to take precedence over Per…nvd · 2026-07-08
mediumCVE-2026-59998: sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAccept…nvd · 2026-07-08
mediumCVE-2026-59997: internal-sftp in sshd in OpenSSH before 10.4 recognizes only the first 9 command-line argument…nvd · 2026-07-08
mediumCVE-2026-59999: In sshd in OpenSSH before 10.4, DisableForwarding=yes was supposed to take precedence over Per…msrc · 2026-07-02