CVE-2026-69760 in Windows
Summary
by MITRE • 09/09/2026
Out-of-bounds read in Windows Kerberos allows an unauthorized attacker to deny service over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described involves a critical out-of-bounds read flaw within the Microsoft Kerberos implementation, which serves as the primary authentication protocol for many enterprise environments relying on Active Directory infrastructure. This specific defect occurs when the Kerberos service processes specially crafted network packets that contain malformed or unexpected data structures. Instead of properly validating the bounds of memory buffers before reading from them, the application accesses memory locations beyond the allocated limits. In high-level security taxonomy, this aligns with CWE-125, which defines out-of-bounds read vulnerabilities where software reads past the end of a buffer. The root cause typically stems from insufficient validation of input data lengths or indices during the parsing of Kerberos tickets or authentication requests, allowing an attacker to trigger memory access violations that disrupt normal system operations.
From an operational perspective, the primary impact of this vulnerability is a denial of service against the affected Windows systems and potentially the broader network infrastructure if critical domain controllers are compromised. When the out-of-bounds read condition is triggered, it often leads to application crashes or kernel-level faults within the security support provider subsystem. This results in the immediate termination of authentication services for users attempting to log on, effectively locking them out of their accounts until the service is restarted or patched. In severe cases, repeated exploitation can cause instability across dependent systems that rely on continuous Kerberos ticket validation, leading to widespread connectivity issues and operational downtime within the organization. The attacker does not require prior access credentials; they only need network-level reachability to send the malicious packets, making this a remote exploit vector that significantly lowers the barrier for entry in terms of initial access requirements.
This vulnerability maps directly to MITRE ATT&CK technique T1498, which covers Network Denial of Service attacks where adversaries disrupt availability by consuming resources or exploiting software flaws. Specifically, it falls under sub-techniques involving exploitation of protocol vulnerabilities rather than simple volumetric flooding. The attack vector is classified as network-based and remote, meaning the attacker can execute this from any location with connectivity to the target port used for Kerberos traffic, typically TCP or UDP 88. There are no additional prerequisites such as user interaction or local access, which elevates the severity rating significantly in risk assessment models like CVSS due to its ease of exploitation and high availability impact.
Mitigation strategies must focus on immediate patching and network segmentation until updates are applied. Organizations should prioritize applying the latest security patches released by Microsoft for their Windows operating systems and Active Directory components, as these typically include fixes that enforce stricter buffer boundary checks in the Kerberos service code. In environments where patching is not immediately feasible, implementing strict firewall rules to restrict access to port 88 from untrusted networks can reduce the attack surface significantly. Additionally, deploying intrusion detection or prevention systems with signatures capable of identifying malformed Kerberos packets may help mitigate active exploitation attempts by dropping suspicious traffic before it reaches the vulnerable service components. Regular auditing of network logs for unusual authentication failures or system crashes related to security packages is also recommended to detect potential probing activities early in the kill chain.