CVE-2026-78319 in modu680-AS
Summary
by MITRE • 09/01/2026
A service running on the affected products contains a potential Time-of-Check Time-of-Use (TOCTOU) race condition. An unauthenticated remote attacker could exploit this race condition to bypass intended security controls. This may result in the execution of unauthorized code.
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Analysis
by VulDB Data Team • 09/01/2026
The identified vulnerability represents a classic Time-of-Check Time-of-Use, or TOCTOU, race condition within a service operating on the affected products. This class of flaw arises when a system performs a check for security conditions and subsequently uses the result of that check to make a critical decision, but fails to ensure that the state remains unchanged between these two operations. In this specific instance, an unauthenticated remote attacker can exploit the timing gap by manipulating file systems or resource states concurrently with the service's validation logic. By rapidly alternating requests or modifying resources in parallel threads, the attacker forces the system into a state where the initial check passes under one set of conditions, but the subsequent use occurs under different, maliciously crafted conditions. This discrepancy allows the attacker to bypass intended security controls that were designed to restrict access or validate inputs before execution.
From a technical perspective, TOCTOU vulnerabilities are particularly insidious because they rely on non-atomic operations and race conditions rather than logical errors in code syntax. The service likely retrieves information about a resource, such as checking file permissions or verifying the existence of a configuration file, and then proceeds to act upon that resource based on the retrieved data. If an attacker can modify the underlying resource between the check and the use phases, they can trick the application into operating on unauthorized or maliciously altered objects. This mechanism effectively neutralizes access control mechanisms because the security boundary is breached not by breaking encryption or bypassing authentication protocols directly, but by exploiting the temporal inconsistency in how the system validates and processes resources.
The operational impact of this vulnerability is severe, as it enables an unauthenticated remote attacker to execute unauthorized code on the target system. Since no prior authentication is required, the attack surface is maximized, allowing any network-accessible entity to attempt exploitation. Successful exploitation could lead to full system compromise, including data theft, modification of critical configurations, or use of the compromised host as a pivot point for further attacks within the internal network. The ability to execute arbitrary code undermines the integrity and availability of the service, potentially leading to denial-of-service conditions if malicious payloads disrupt normal operations, or creating persistent backdoors that allow long-term unauthorized access.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-367, which defines TOCTOU race conditions in security-critical programs where a check is performed and then the result of the check is used without ensuring consistency. Furthermore, from an offensive perspective, this exploitation technique maps to MITRE ATT&CK tactic T1059, Command and Scripting Interpreter, specifically through techniques that leverage system binaries or scripts for unauthorized execution. It also relates to privilege escalation vectors where initial access leads to higher-level control due to flawed validation logic.
Mitigation strategies must focus on eliminating the race condition window by ensuring atomic operations wherever possible. Developers should refactor the affected code to perform checks and subsequent actions in a single, indivisible operation, thereby preventing state changes between verification and execution. Utilizing file locking mechanisms or operating system primitives that guarantee exclusive access during critical sections can also mitigate this risk. Additionally, implementing strict input validation and adopting a principle of least privilege for service accounts reduces the potential impact if an exploit is attempted. Regular security audits focusing on concurrency issues and race conditions are essential to identify similar flaws in other components of the software stack before they can be leveraged by adversaries.