CVE-2026-88158 in Windows
Summary
by MITRE • 10/14/2026
Out-of-bounds read in Microsoft Digest Authentication allows an authorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified as an out-of-bounds read within the Microsoft Digest Authentication mechanism represents a critical memory safety flaw that compromises the integrity of local system data. This specific defect occurs when the authentication module processes input parameters without adequately validating buffer boundaries, leading to a scenario where the application attempts to access memory locations beyond the allocated limits of a designated array or string structure. In the context of network protocols and operating system services, such as those handled by Microsoft's implementation of HTTP Digest Authentication, precise boundary checks are essential to prevent unauthorized data exposure. When these checks fail, the software may read sensitive information from adjacent memory regions that were not intended for disclosure during the authentication handshake process.
From a technical perspective, this flaw aligns with Common Weakness Enumeration category CWE-125, which describes out-of-bounds read vulnerabilities. The root cause typically stems from improper calculation of buffer sizes or failure to verify input length against expected maximum limits before performing memory copy operations. An attacker who has already authenticated locally can exploit this condition by crafting specific requests that trigger the erroneous memory access. Because Digest Authentication relies on challenge-response mechanisms involving hashed credentials, any leakage of internal state information could potentially aid in further attacks, although the primary impact here is the disclosure of local system data rather than immediate remote code execution or privilege escalation.
The operational impact of this vulnerability centers on confidentiality loss for authorized users within the affected environment. Since exploitation requires prior authentication, the threat actor must already possess valid credentials to interact with the vulnerable service. Once authenticated, however, they can leverage the out-of-bounds read to extract arbitrary memory contents from the process space hosting the authentication component. This could include sensitive configuration details, cached tokens, or other proprietary data stored in adjacent memory blocks. While this does not directly allow for control flow hijacking due to its read-only nature, it significantly degrades the security posture by enabling information gathering that can facilitate subsequent lateral movement or deeper system compromise.
In terms of threat modeling and adversary behavior, this vulnerability maps to techniques observed in the MITRE ATT&CK framework under data exfiltration categories, specifically those involving local application-specific mechanisms. Attackers often utilize such flaws as part of a broader campaign to gather intelligence about the target environment before proceeding with more destructive actions. The ability to read arbitrary memory locations provides valuable context that can be used to identify running processes, loaded modules, or other security controls active on the host system. This aligns with standard post-exploitation behaviors where reconnaissance is conducted using native tools and inherent software weaknesses rather than external malware implants.
Mitigation strategies for this vulnerability primarily involve applying vendor-provided patches that address the underlying memory management errors in the Digest Authentication implementation. Organizations should prioritize updating affected systems to versions where boundary checks have been rigorously enforced and input validation has been strengthened. Additionally, implementing strict access controls and least-privilege principles can limit the potential impact if an attacker gains initial foothold through other means. Network segmentation and monitoring for anomalous authentication patterns may also help detect attempts to exploit this flaw before significant data loss occurs. Regular security assessments and code reviews focusing on memory safety are recommended to prevent similar vulnerabilities in future software updates.