CVE-2026-107027 in Tarnhelm
Summary
by MITRE • 10/29/2026
Insecure permissions in lz233 Tarnhelm v1.8.2 (versionCode 20250630) allows unauthorized attackers to invoke an exported component, leading to arbitrary data access and overwriting.
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Analysis
by VulDB Data Team • 10/29/2026
The vulnerability identified in lz233 Tarnhelm version 1.8.2, specifically associated with build code 20250630, stems from a critical misconfiguration of Android application permissions regarding exported components. In the context of mobile operating systems like Android, an exported component is one that can be invoked by other applications installed on the same device or even by external entities if network accessibility is granted. The core technical flaw lies in the failure to enforce strict access controls on these exposed interfaces. When a developer marks an activity, service, receiver, or provider as exported without implementing appropriate permission checks or signature-based verification mechanisms, they effectively create an open door for any application running on the device to interact with it. This architectural oversight transforms what should be internal logic into a publicly accessible entry point that lacks authentication and authorization barriers.
From a technical perspective, this misconfiguration directly facilitates unauthorized invocation of sensitive functions within the Tarnhelm application. An attacker can craft malicious intents or direct calls to these exported components without needing legitimate credentials or system privileges. The operational impact is severe because it allows for arbitrary data access and potential overwriting of critical information stored by the application. This means that confidential user data, such as authentication tokens, personal identifiers, or sensitive configuration files managed by Tarnhelm, can be read by malicious third-party apps. Furthermore, the ability to overwrite data implies that an attacker could corrupt the state of the application, potentially leading to denial of service conditions or manipulating security settings to further weaken the device's defense posture.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) category CWE-269, which addresses Improper Privilege Context Management, and more specifically CWE-732, which relates to Incorrect Permission Assignment for Critical Resource. In terms of offensive security frameworks, this flaw enables techniques categorized under MITRE ATT&CK Mobile as T1504, Weak or Unprotected Credentials, although the primary vector here is architectural rather than credential-based. It also facilitates lateral movement within a compromised device ecosystem by allowing one malicious app to compromise another trusted application through shared exported interfaces. The lack of signature-level verification means that even apps with lower security ratings can exploit this weakness against higher-security applications if they share the same user space.
To mitigate this risk, developers must immediately audit all AndroidManifest.xml declarations for components marked as android:exported=true. Each such component should be evaluated to determine if external access is strictly necessary; if not, it should be set to false. If external access is required, robust permission checks must be implemented using the checkCallingPermission or checkSelfPermission methods within the code logic of those components. Additionally, leveraging signature-level permissions ensures that only applications signed with the same certificate as Tarnhelm can invoke these components, effectively neutralizing attacks from unrelated malicious apps. Regular static analysis and dynamic testing during the development lifecycle are essential to detect such permission misconfigurations before deployment. Users should also ensure they keep their devices updated and review app permissions regularly to minimize exposure to potential exploitation vectors arising from poorly secured applications in their ecosystem.