Affects Microsoft Active Directory Certificate Services, a widely deployed Windows Server role; privilege escalation can impact enterprise identity and domain security.
CVE-2026-54121
AD CS improper authorization allows authenticated users to escalate privileges over the network.
Is CVE-2026-54121 being exploited?
Not confirmed. CVE-2026-54121 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 1.8% probability of exploitation in the next 30 days.
How severe is CVE-2026-54121?
CVE-2026-54121 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-54121?
Yes. A fix has been recorded for CVE-2026-54121. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-54121 affect?
CVE-2026-54121 affects Microsoft Active Directory Certificate Services (AD CS) on Windows Server. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-54121?
Apply vendor patch when released; restrict AD CS access, harden permissions, and monitor certificate/auth logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated attacker can elevate privileges via AD CS over the network, potentially gaining higher domain/admin control and compromising identity services.
Immediate action required
- affected>= 10.0.14393.0 and < 10.0.14393.9339
- affected>= 10.0.17763.0 and < 10.0.17763.9020
- affected>= 6.2.9200.0 and < 6.2.9200.26226
- affected>= 6.3.9600.0 and < 6.3.9600.23291
- affected>= 6.3.9600.0 and < 6.3.9600.23291
- affected>= 6.2.9200.0 and < 6.2.9200.26226
- affected>= 10.0.14393.0 and < 10.0.14393.9339
- affected>= 10.0.14393.0 and < 10.0.14393.9339
- affected>= 10.0.17763.0 and < 10.0.17763.9020
- affected>= 10.0.17763.0 and < 10.0.17763.9020
- affected>= 10.0.20348.0 and < 10.0.20348.5386
- affected>= 10.0.26100.0 and < 10.0.26100.33158
- affected>= 10.0.26100.0 and < 10.0.26100.33158
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.