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CheckSum is a privilege-escalation vulnerability in Windows Kerberos affecting protocol transition and constrained delegation flows. The flaw is described as a missing cryptographic verification step combined with a downgrade condition in the Key Distribution Center (KDC), allowing a maliciously crafted TGS-REQ to be accepted with an unkeyed checksum. In the described attack path, an attacker targets a service account configured for protocol transition with TrustedToAuthForDelegation enabled, forges identity data for a privileged user in the S4U-related request structure, and submits the malformed request to the domain controller. Because the vulnerable KDC accepts the downgraded or insufficiently protected checksum, it issues a service ticket asserting the forged privileged identity. That forged ticket can then be used as an evidence ticket in an S4U2proxy constrained delegation request to obtain a backend service ticket as the impersonated user.
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What an attacker gets, and what they’ve been doing with it.
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No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
11 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Kerberos delegation attack technique/vulnerability (named CheckSum) that can leave sensitive Active Directory computer accounts (Tier 0 / machine identities) delegable by default, creating a delegation hardening blind spot.
A vulnerability in the Kerberos constrained delegation mechanism, named CheckSum, allows attackers to hijack temporary delegations and gain domain admin rights. Patched as CVE-2025-60704.
A Kerberos KDC downgrade flaw affecting protocol transition and constrained delegation that allows an attacker to forge service tickets for a high-privileged user and obtain delegated access to backend services.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.