# Windows Kerberos elevation of privilege

Source: https://startwithidentity.com/cves/cve-2026-20849/
Last updated: 2026-08-29
License: content by Start with Identity. Cite the source URL.

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## What broke

Microsoft patched a Windows Kerberos elevation of privilege as CVE-2026-20849. High severity. Public write-ups are thinner than KerberLoss or ResetNightmare. Treat it as part of the same 2026 KDC patch train.

## Why it matters

Kerberos EoP on a DC is never a workstation-only ticket. If you are already bundling [CVE-2026-25177](https://startwithidentity.com/cves/cve-2026-25177/) and [CVE-2026-27912](https://startwithidentity.com/cves/cve-2026-27912/), add this ID so change-management does not split the train.

## What to do

- Deploy the named Microsoft update on every DC.
- Confirm with `Get-HotFix` / your patch report, not with "we did February."
- After patching, watch for unusual TGT / TGS patterns. KDC bugs sometimes leave noisy exploit attempts in the security log.

## After you patch

Active Directory compromise is not contained by patching, because the artifacts an attacker creates outlive the vulnerability.

- **Rotate the krbtgt account twice**, with the replication interval between rotations, if there is any indication of ticket forgery. One rotation is not enough.
- **Audit AD CS certificate templates** for enrolment and enrollee-supplied-subject permissions, which are the most common escalation path left behind. See [certificate lifecycle](https://startwithidentity.com/glossary/certificate-lifecycle/).
- **Review privileged group membership and delegation rights** (Domain Admins, DnsAdmins, constrained and resource-based constrained delegation) for changes during the window.
- **Hunt for tickets with anomalous lifetimes or encryption types**, and for authentications to services that identity never touches.
- **Treat any issued certificate as a durable credential**: revoking a user's password does not revoke a certificate that authenticates as them. See [privilege escalation](https://startwithidentity.com/glossary/privilege-escalation/) and [lateral movement](https://startwithidentity.com/glossary/lateral-movement/).

## Sources

- [NVD: CVE-2026-20849](https://nvd.nist.gov/vuln/detail/CVE-2026-20849)