CVE-2026-69676 in Windows
Summary
by MITRE • 09/09/2026
Authentication bypass by capture-replay in Windows Kerberos allows an authorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described represents a critical authentication bypass mechanism within the Microsoft Windows Kerberos implementation, specifically leveraging the technique known as kerberoasting or more accurately in this context, credential replay attacks against pre-authentication mechanisms. This flaw allows an authenticated user who has captured valid Kerberos tickets to reuse them for unauthorized access, effectively circumventing the intended security controls that rely on the uniqueness and temporal validity of authentication tokens. The core technical issue lies in the handling of Ticket Granting Tickets (TGTs) or service tickets where the system fails to adequately enforce strict replay detection policies under specific network conditions or configuration states. By capturing these encrypted ticket structures during transit, an attacker can inject them back into the authentication flow at a later time, tricking the Key Distribution Center or target service into accepting the stale credentials as if they were freshly issued for a current session.
From a technical perspective, this vulnerability exploits weaknesses in how Kerberos handles timestamp validation and sequence numbers within its Asymmetric Cryptography Standard Profile messages. While Kerberos is designed to be resistant to replay attacks through the inclusion of timestamps that must fall within an acceptable skew window, certain implementations or misconfigurations may allow for extended windows or fail to properly invalidate tickets after a single use in specific service contexts. The attacker leverages this by intercepting the initial authentication exchange using tools capable of network packet capture and manipulation. Once the encrypted ticket is obtained, it can be replayed against services that do not strictly enforce one-time usage policies or where the session state does not track previously consumed tickets effectively. This bypasses multi-factor authentication requirements if the second factor was tied to the initial login event rather than continuously verified during each service access attempt.
The operational impact of this vulnerability is severe, as it directly compromises the integrity of identity-based access controls across Windows domains and cloud environments integrated with Azure Active Directory or other federated services. An attacker who successfully exploits this flaw can gain persistent unauthorized access to sensitive systems without needing to crack passwords or exploit additional software flaws. This facilitates lateral movement within a network, allowing the adversary to escalate privileges by accessing high-value service accounts that have been compromised through ticket replay. The ability to execute code over a network using these stolen credentials means that malware deployment, data exfiltration, and further reconnaissance activities can proceed undetected for extended periods, as the activity appears legitimate from an authentication standpoint.
Mitigation strategies must focus on both technical controls and architectural changes to reduce reliance on vulnerable Kerberos configurations. Organizations should immediately enforce strict time synchronization across all domain controllers and client machines to minimize the acceptable timestamp skew window, thereby reducing the validity period during which a captured ticket can be replayed. Implementing Conditional Access policies that require continuous authentication or step-up verification for sensitive resources is crucial. Additionally, enabling Advanced Audit Policy settings to log Kerberos events with high verbosity allows security teams to detect anomalous patterns indicative of replay attacks, such as repeated use of the same Ticket Granting Ticket from different source IP addresses. Upgrading to newer versions of Windows that include enhanced protections against kerberoasting and enforcing AES-256 encryption for all Kerberos traffic can also significantly raise the barrier for attackers attempting to exploit this flaw.
This vulnerability aligns with Common Weakness Enumeration (CWE) ID 384, which describes Session Fixation, although in this specific context it is more accurately mapped to CWE 290: Authentication Bypass by Spoofing or CWE 617: Reachable Assertion Failure if the root cause involves a failure in state validation. In terms of attack tactics, this behavior corresponds directly to MITRE ATT&CK technique T1550.003, known as Pass the Ticket, where adversaries steal and reuse Kerberos tickets to impersonate users or services without needing their passwords. It also intersects with T1078 Valid Accounts, as the attacker utilizes legitimate but stolen credentials to maintain access. Security teams should prioritize monitoring for unusual Kerberos ticket usage patterns and ensure that all systems are patched against known vulnerabilities in the Windows authentication stack to prevent exploitation of this replay-based bypass mechanism.