CVE-2026-108398 in .NET Framework
Summary
by MITRE • 10/14/2026
Untrusted search path in .NET Framework allows an authorized attacker to bypass a security feature locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a classic untrusted search path flaw within the Microsoft .NET Framework, representing a significant local privilege escalation risk for systems running affected versions of this runtime environment. This type of weakness arises when software constructs file paths using user-controlled input or relies on system directories that are not properly secured against modification by lower-privileged users. In the context of the .NET Framework, this typically manifests when an application or service attempts to load dynamic link libraries (DLLs) or other executable components from a directory where unauthorized processes can write new files or modify existing ones. Because Windows operating systems search for DLLs in a specific order before checking the system directory, if a vulnerable component searches directories such as the current working directory of the launching process or user-writable paths prior to secure system locations, an attacker with local access can exploit this sequence.
From a technical perspective, the core issue lies in the failure to enforce strict path validation and security descriptors on the directories used for dynamic loading. When an authorized but potentially malicious actor gains foothold within the environment, they can place a specially crafted DLL into one of these searched locations. If the vulnerable .NET application subsequently attempts to load this component, it will inadvertently execute the attacker's code instead of the legitimate library. This mechanism allows the attacker to hijack the execution flow of the privileged process running under their user context or potentially higher privileges if the service is configured with elevated permissions. The exploitation does not require remote access or complex network interactions; rather, it leverages local file system manipulation and the inherent trust placed in the runtime environment by the operating system's loader.
The operational impact of this vulnerability is severe, as it effectively neutralizes standard isolation boundaries between user accounts and privileged services. An attacker who exploits this flaw can achieve arbitrary code execution with the security context of the affected application. This often translates to full control over the compromised machine if the vulnerable service runs under a high-privilege account such as SYSTEM or Administrator. Beyond immediate privilege escalation, this vulnerability facilitates persistent access through DLL hijacking techniques, allowing attackers to maintain their presence on the network and move laterally to other systems without detection by traditional perimeter defenses. The lack of proper input validation regarding file paths means that any application relying on these unsafe loading practices is susceptible to compromise, creating a widespread attack surface across enterprise environments utilizing legacy .NET applications.
To mitigate this risk, organizations must implement strict adherence to secure coding standards and system hardening guidelines. Developers should avoid using relative paths for critical library loads and instead use absolute paths or the System32 directory where appropriate. Implementing SafeDllSearchMode is crucial, as it alters the DLL search order to prioritize system directories over user-writable locations like the current working directory. Furthermore, file integrity monitoring solutions can detect unauthorized modifications in sensitive directories, providing an early warning mechanism for potential exploitation attempts. Regular patching of the .NET Framework ensures that known implementation flaws are addressed by Microsoft through security updates. Additionally, applying least-privilege principles to service accounts reduces the impact if a vulnerability is successfully exploited, limiting the scope of damage an attacker can inflict even after gaining initial access through this vector.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-427, which defines uncontrolled search path element as a situation where software does not properly control the location or order in which it searches for resources. In terms of offensive security frameworks, this technique corresponds to ATT&CK tactic T1055, specifically sub-technique 009 known as DLL Search Order Hijacking. Understanding these mappings helps security teams prioritize remediation efforts based on established industry benchmarks and threat intelligence models. By addressing the underlying path validation issues and enforcing secure configuration settings, organizations can significantly reduce their exposure to local privilege escalation attacks targeting .NET-based applications.